Acoustic wave device structure, integrated structure of power amplifier and acoustic wave device

ABSTRACT

An integrated structure of power amplifier and acoustic wave device comprises: a compound semiconductor epitaxial substrate including an epitaxial structure formed on a compound semiconductor substrate, a power amplifier upper structure formed on a top-side of a left part of the compound semiconductor epitaxial substrate, and a film bulk acoustic resonator formed on the top-side of a right part of the compound semiconductor epitaxial substrate; wherein the left part of the compound semiconductor epitaxial substrate and the power amplifier upper structure form a power amplifier; the right part of the compound semiconductor epitaxial substrate and the film bulk acoustic resonator form an acoustic wave device; the integrated structure of power amplifier and acoustic wave device on the same compound semiconductor epitaxial substrate is capable of reducing the component size, optimizing the impedance matching, and reducing the signal loss between power amplifier and acoustic wave device.

CROSS-REFERENCE TO RELATED DOCUMENTS

The present invention is a divisional application of U.S. patentapplication Ser. No. 14/586,592 entitled “IMPROVED ACOUSTIC WAVE DEVICESTRUCTURE, INTEGRATED STRUCTURE OF POWER AMPLIFIER AND ACOUSTIC WAVEDEVICE, AND FABRICATION METHODS THEREOF” filed on Dec. 30, 2014.

FIELD OF THE INVENTION

The present invention relates to an integrated structure of poweramplifier and acoustic wave device, wherein the integrated structure ofthe power amplifier and the acoustic wave device on the same compoundsemiconductor epitaxial substrate is capable of reducing the componentsize, optimizing the impedance matching, and reducing the signal lossbetween the power amplifier and the acoustic wave device.

BACKGROUND OF THE INVENTION

Please refer to FIG. 7˜7D, which are the schematics of conventionalproduction processes of acoustic wave device. First, forming a recess702 on a silicon substrate 701; then forming a protection layer 703 onthe silicon substrate 701 and the recess 702; and then forming aphosphosilicate glass (PSG) layer 705 on the protection layer 703 suchthat the phosphosilicate glass (PSG) layer 705 at least filled therecess 702; then polishing to remove the phosphosilicate glass (PSG)layer 705 outside the recess 702 by chemical mechanical polishing (CMP).Forming an acoustic wave device 710 with metal 711—insulator 712—metal713 structure above the recess 702 such that the two ends of theacoustic wave device 710 with metal 711—insulator 712—metal 713structure across outside of the recess 702; removing the rest of thephosphosilicate glass (PSG) layer 705 within the recess 702 such thatthe recess 702 forms a cavity.

Conventional technical producing the acoustic wave device needs to applychemical mechanical polishing (CMP) technique for polishing to removethe phosphosilicate glass (PSG) layer 705 outside the recess 702.Furthermore the polishing requires fine polishing such that theroughness of polished surface is very smooth. Otherwise, the formationof the acoustic wave device 710 with metal 711—insulator 712—metal 713structure will be influenced by the roughness of the polished surface.However the fine polished surface requirement for chemical mechanicalpolishing (CMP) process, not only the cost of the equipment is veryexpensive but also the time consuming and the materials cost are veryhigh, such that the cost of production is too high.

Furthermore, the design of the single recess 702 has the problem thatthe gap between the bottom of the acoustic wave device 710 and thebottom of the recess 702 cannot efficiently widen. Hence, when theacoustic wave device 710 is affected by stress such that the acousticwave device 710 is bended downwardly, the bottom of the acoustic wavedevice 710 may easily contact with the bottom of the recess 702 suchthat the characteristics of the acoustic wave device 710 been affected.

On the other hand, the application of the acoustic wave device 710 isoften used as a radio frequency signal filter. When the application iswith the power amplifier, the acoustic wave device plays a role tofilter the signal firstly and then transmits the filtered signal to thepower amplifier; or the power amplifier amplifies the signal firstly andthen transmits the amplified signal to the acoustic wave device forfiltering. However, the conventional acoustic wave device design isusually based on the silicon substrate. There is no one who ever triesto integrate the acoustic wave device with the compound semiconductorpower amplifier on the same compound semiconductor epitaxial substrate.Integrating the acoustic wave device and the power amplifier on the samecompound semiconductor epitaxial substrate may reduce the componentsize, and optimize the impedance matching, and reduce the signal lossbetween the power amplifier and the acoustic wave device.

Accordingly, the inventor has developed the design which may effectivelywiden the gap between the bottom of the acoustic wave device and thebottom of the recess, also may integrate the acoustic wave device andthe power amplifier on the same compound semiconductor epitaxialsubstrate with the above mentioned benefits, the advantage of low cost,and with reduced component size, the optimized impedance matching, andthe reduced signal loss between the power amplifier and the acousticwave device.

SUMMARY OF THE INVENTION

There are two technical problems the present invention desires tosolve: 1. How to provide a design which may effectively widen the gapbetween the bottom of the acoustic wave device and the bottom of therecess? 2. How to integrate the acoustic wave device and the poweramplifier on the same compound semiconductor epitaxial substrate suchthat the component size is reduced, the impedance matching is optimized,and the signal loss between the power amplifier and the acoustic wavedevice is reduced?

To solve the above technical problems to achieve the expected effect,the present invention provides an integrated structure of poweramplifier and acoustic wave device, which comprises: a compoundsemiconductor epitaxial substrate, a power amplifier upper structure anda film bulk acoustic resonator; wherein said compound semiconductorepitaxial substrate includes a compound semiconductor substrate and anepitaxial structure formed on said compound semiconductor substrate;said power amplifier upper structure is formed on a top-side of a leftpart of said compound semiconductor epitaxial substrate, wherein saidleft part of said compound semiconductor epitaxial substrate and saidpower amplifier upper structure form a power amplifier; said film bulkacoustic resonator is formed on the top-side of a right part of saidcompound semiconductor epitaxial substrate, wherein said right part ofsaid compound semiconductor epitaxial substrate and said film bulkacoustic resonator form an acoustic wave device; wherein, the integratedstructure of said power amplifier and said acoustic wave device on thesame said compound semiconductor epitaxial substrate is capable ofreducing the component size, optimizing the impedance matching, andreducing the signal loss between said power amplifier and said acousticwave device.

In an embodiment, said compound semiconductor substrate is made of GaAs,SiC, InP, GaN, AlN or Sapphire.

In an embodiment, said film bulk acoustic resonator comprises: asupporting layer and a bulk acoustic resonator structure; wherein saidsupporting layer is formed on said compound semiconductor epitaxialsubstrate, wherein said supporting layer has a supporting layer recesson the bottom of said supporting layer, said supporting layer has anupwardly protruding supporting layer mesa right above said supportinglayer recess, and wherein said compound semiconductor epitaxialsubstrate has a substrate recess on the top of said compoundsemiconductor epitaxial substrate, said substrate recess is locatedright below said supporting layer recess, said supporting layer recessis communicated with said substrate recess, and said supporting layerrecess and said substrate recess have a boundary therebetween and theboundary is the extended from the top surface of said compoundsemiconductor epitaxial substrate; wherein said bulk acoustic resonatorstructure is formed on said supporting layer, said bulk acousticresonator structure includes: a bottom electrode, a dielectric layer anda top electrode; wherein said bottom electrode is formed on one end ofsaid supporting layer, where said bottom electrode is formed on and atleast extended along said supporting layer mesa; wherein said dielectriclayer is formed at least on said bottom electrode above said supportinglayer mesa; wherein said top electrode is formed on the other end withrespect to said bottom electrode, where said top electrode is formed onsaid dielectric layer or formed on both said dielectric layer and saidsupporting layer, and said top electrode is formed on and at leastextended along said dielectric layer above said supporting layer mesa;wherein the gap between said supporting layer mesa and the bottom ofsaid substrate recess is increased by the communication of saidsupporting layer recess and said substrate recess, so as to avoid thecontact of said supporting layer mesa and the bottom of said substraterecess when said film bulk acoustic resonator is affected by stress suchthat said supporting layer mesa is bended downwardly.

In an embodiment, said supporting layer recess has a depth between 10 nmand 3500 nm.

In an embodiment, the optimized depth of said supporting layer recess isbetween 10 nm and 1500 nm.

In an embodiment, said supporting layer recess has an opening smallerthan or almost equal to that of said substrate recess.

In an embodiment, said film bulk acoustic resonator further comprises atleast one etching recess, one end of said at least one etching recess iscommunicated with said supporting layer recess, the other end of said atleast one etching recess penetrates said supporting layer or penetratesboth said supporting layer and said bulk acoustic resonator structuresuch that said at least one etching recess is communicated with theoutside, and thereby said supporting layer recess is communicated withthe outside.

In an embodiment, said power amplifier is a heterojunction bipolartransistor (HBT).

In an embodiment, said epitaxial structure includes: a subcollectorlayer and a collector layer; wherein said subcollector layer is formedon said compound semiconductor substrate; said collector layer is formedon said subcollector layer.

In an embodiment, said substrate recess is peripherally surrounded bysaid collector layer, and the bottom of said substrate recess is saidsubcollector layer.

In an embodiment, said collector layer is made of GaAs.

In an embodiment, said collector layer has a thickness between 500 nmand 3000 nm.

In an embodiment, said left part of said compound semiconductorepitaxial substrate further comprises a collector recess, the bottom ofsaid collector recess is said subcollector layer, and wherein said poweramplifier upper structure includes: a base layer, an emitter ledgelayer, an emitter layer, a base electrode, an emitter electrode and acollector electrode; wherein said base layer is formed on said collectorlayer; said emitter ledge layer is formed on said base layer; saidemitter layer is formed on said emitter ledge layer; said base electrodeis formed on said base layer and/or said emitter ledge layer; saidemitter electrode is formed on said emitter layer; said collectorelectrode is formed on said subcollector layer within said collectorrecess; thereby said left part of said compound semiconductor epitaxialsubstrate includes: said compound semiconductor substrate, saidsubcollector layer, said collector layer and said collector recess;wherein said left part of said compound semiconductor epitaxialsubstrate and said power amplifier upper structure form saidheterojunction bipolar transistor.

In an embodiment, said base layer is made of GaAs.

In an embodiment, said base layer has a thickness between 60 nm and 100nm.

In an embodiment, said epitaxial structure further comprises an etchingstop layer, wherein said etching stop layer is formed on saidsubcollector layer, and said collector layer is formed on said etchingstop layer, wherein the bottom of said collector recess is saidsubcollector layer, said collector electrode is formed on saidsubcollector layer within said collector recess.

In an embodiment, said substrate recess is peripherally surrounded bysaid collector layer and said etching stop layer, and the bottom of saidsubstrate recess is said subcollector layer.

In an embodiment, said etching stop layer is made of InGaP.

In an embodiment, said etching stop layer has a thickness between 5 nmand 1000 nm.

In an embodiment, the optimized thickness of said etching stop layer is20 nm.

In an embodiment, said power amplifier is a field effect transistor(FET), a high electron mobility transistor (HEMT) or a pseudomorphichigh electron mobility transistor (pHEMT).

In an embodiment, said epitaxial structure includes: a buffer layer, achannel layer, a Schottky layer and a cap layer; wherein said bufferlayer is formed on said compound semiconductor substrate; said channellayer is formed on said buffer layer; said Schottky layer is formed onsaid channel layer; said cap layer is formed on said Schottky layer.

In an embodiment, the bottom of said substrate recess is said bufferlayer, and said substrate recess is peripherally surrounded by saidchannel layer, said Schottky layer and said cap layer or by said bufferlayer, said channel layer, said Schottky layer and said cap layer.

In an embodiment, said left part of said compound semiconductorepitaxial substrate further comprises a gate recess; the bottom of saidgate recess is said Schottky layer; and wherein said power amplifierupper structure includes: a drain electrode, a source electrode and agate electrode; wherein said drain electrode is formed on one end ofsaid cap layer; said source electrode is formed on the other end of saidcap layer, wherein said gate recess is located between said drainelectrode and said source electrode; said gate electrode is formed onsaid Schottky layer within said gate recess; thereby said left part ofsaid compound semiconductor epitaxial substrate includes: said compoundsemiconductor substrate, said buffer layer, said channel layer, saidSchottky layer, said cap layer and said gate recess; wherein said leftpart of said compound semiconductor epitaxial substrate and said poweramplifier upper structure form said pseudomorphic high electron mobilitytransistor.

In addition, the present invention further provides an improved acousticwave device structure, which comprises: a substrate and a film bulkacoustic resonator; wherein said substrate has a substrate recess on thetop of said substrate; said film bulk acoustic resonator formed on saidsubstrate, wherein said film bulk acoustic resonator includes: asupporting layer and a bulk acoustic resonator structure; wherein saidsupporting layer is formed on said substrate, wherein said supportinglayer has a supporting layer recess on the bottom of said supportinglayer, said supporting layer has an upwardly protruding supporting layermesa right above said supporting layer recess, and said supporting layerrecess is located right above said substrate recess, said supportinglayer recess is communicated with said substrate recess, and saidsupporting layer recess and said substrate recess have a boundarytherebetween and the boundary is the extended from the top surface ofsaid substrate; bulk acoustic resonator structure is formed on saidsupporting layer, wherein said bulk acoustic resonator structureincludes: a bottom electrode, a dielectric layer and a top electrode;wherein said bottom electrode is formed on one end of said supportinglayer, where said bottom electrode is formed on and at least extendedalong said supporting layer mesa; said dielectric layer is formed atleast on said bottom electrode above said supporting layer mesa; saidtop electrode is formed on the other end with respect to said bottomelectrode, where said top electrode is formed on said dielectric layeror formed on both said dielectric layer and said supporting layer, andsaid top electrode is formed on and at least extended along saiddielectric layer above said supporting layer mesa; wherein the gapbetween said supporting layer mesa and the bottom of said substraterecess is increased by the communication of said supporting layer recessand said substrate recess, so as to avoid the contact of said supportinglayer mesa and the bottom of said substrate recess when said film bulkacoustic resonator is affected by stress such that said supporting layermesa is bended downwardly.

In an embodiment, said film bulk acoustic resonator further comprises atleast one etching recess, one end of said at least one etching recess iscommunicated with said supporting layer recess, the other end of said atleast one etching recess penetrates said supporting layer or penetratesboth said supporting layer and said bulk acoustic resonator structuresuch that said at least one etching recess is communicated with theoutside, and thereby said supporting layer recess is communicated withthe outside.

In an embodiment, said supporting layer recess has an opening smallerthan or almost equal to that of said substrate recess.

In an embodiment, said substrate includes a base substrate and anepitaxial structure formed on said base substrate.

In an embodiment, said base substrate is made of GaAs, SiC, InP, GaN,AlN, Sapphire, Si or glass.

In an embodiment, said epitaxial structure includes: a buffer layer, anetching stop layer and a bottom sacrificial layer; wherein said bufferlayer is formed on said base substrate; said etching stop layer isformed on said buffer layer; said bottom sacrificial layer is formed onsaid etching stop layer; wherein said substrate recess is peripherallysurrounded by said bottom sacrificial layer, and the bottom of saidsubstrate recess is said etching stop layer.

In an embodiment, said bottom sacrificial layer is made of GaAs.

In an embodiment, said bottom sacrificial layer has a thickness between500 nm and 3000 nm.

In an embodiment, said etching stop layer is made of InGaP.

In an embodiment, said etching stop layer has a thickness between 5 nmand 1000 nm.

In an embodiment, the optimized thickness of said etching stop layer is20 nm.

In an embodiment, said substrate is made of a silicon substrate.

In an embodiment, said supporting layer recess has a depth between 10 nmand 2500 nm.

In an embodiment, the optimized depth of said supporting layer recess isbetween 10 nm and 50 nm.

For further understanding the characteristics and effects of the presentinvention, some preferred embodiments referred to drawings are in detaildescribed as follows.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1˜1B are the cross-sectional views of embodiments of the integratedstructure of power amplifier and acoustic wave device of the presentinvention.

FIG. 1C-1H are the cross-sectional schematics showing steps of afabrication method for the embodiments of the integrated structure ofpower amplifier and acoustic wave device of the present invention.

FIGS. 1I and 1J are the partial enlarged cross-sectional views ofembodiments of the integrated structure of power amplifier and acousticwave device of the present invention.

FIG. 1K˜1N are the top views showing the relative position of theetching recess and the supporting layer mesa in the embodiments of theintegrated structure of power amplifier and acoustic wave device of thepresent invention.

FIG. 2˜2E are the cross-sectional views of embodiments of the integratedstructure of power amplifier and acoustic wave device of the presentinvention.

FIG. 2F˜2W are the cross-sectional schematics showing steps of afabrication method for the embodiments of the integrated structure ofpower amplifier and acoustic wave device of the present invention.

FIG. 3˜3C are the cross-sectional views of embodiments of the integratedstructure of power amplifier and acoustic wave device of the presentinvention.

FIG. 3D˜3O are the cross-sectional schematics showing steps of afabrication method for the embodiments of the integrated structure ofpower amplifier and acoustic wave device of the present invention.

FIG. 4˜4B are the cross-sectional views of embodiments of the improvedacoustic wave device structure of the present invention.

FIGS. 4C and 4D are the partial enlarged cross-sectional views ofembodiments of the improved acoustic wave device structure of thepresent invention.

FIG. 4E˜4H are the top views showing the relative position of theetching recess and the supporting layer mesa in the embodiments of theimproved acoustic wave device structure of the present invention.

FIG. 5˜5C are the cross-sectional views of embodiments of the improvedacoustic wave device structure of the present invention.

FIG. 5D˜5M are the cross-sectional schematics showing steps of afabrication method for the embodiments of the improved acoustic wavedevice structure of the present invention.

FIGS. 6 and 6A are the cross-sectional views of an embodiment of theimproved acoustic wave device structure of the present invention.

FIG. 6B˜6L are the cross-sectional schematics showing steps of afabrication method for the embodiments of the improved acoustic wavedevice structure of the present invention.

FIGS. 6M and 6N are the cross-sectional views of an embodiment of theimproved acoustic wave device structure of the present invention.

FIGS. 6M and 6N are the schematics of conventional production processesof acoustic wave device.

DETAILED DESCRIPTIONS OF PREFERRED EMBODIMENTS

Please refer to FIG. 1, the cross-sectional view of an embodiment of theintegrated structure of power amplifier and acoustic wave device of thepresent invention, the integrated structure comprises: a compoundsemiconductor epitaxial substrate 10, a power amplifier upper structure21 and a film bulk acoustic resonator 51. The compound semiconductorepitaxial substrate 10 includes a compound semiconductor substrate 12and an epitaxial structure 13 formed on the compound semiconductorsubstrate 12. The power amplifier upper structure 21 is formed on atop-side of a left part 101 of the compound semiconductor epitaxialsubstrate 10, wherein the left part 101 of the compound semiconductorepitaxial substrate 10 and the power amplifier upper structure 21 form apower amplifier 20. The film bulk acoustic resonator 51 is formed on thetop-side of a right part 102 of the compound semiconductor epitaxialsubstrate 10, wherein the right part 102 of the compound semiconductorepitaxial substrate 10 and the film bulk acoustic resonator 51 form anacoustic wave device 50. The integrated structure 1 of the poweramplifier 20 and the acoustic wave device 50 on the same the compoundsemiconductor epitaxial substrate 10 is capable of reducing thecomponent size, optimizing the impedance matching, and reducing thesignal loss between the power amplifier 20 and the acoustic wave device50.

The film bulk acoustic resonator 51 comprises: a supporting layer 61 anda bulk acoustic resonator structure 60. The supporting layer 61 isformed on the compound semiconductor epitaxial substrate 10, wherein thesupporting layer 61 has a supporting layer recess 612 on the bottom ofthe supporting layer 61, and the supporting layer 61 has an upwardlyprotruding supporting layer mesa 611 right above the supporting layerrecess 612. The compound semiconductor epitaxial substrate 10 has asubstrate recess 15 on the top of the compound semiconductor epitaxialsubstrate 10, and the substrate recess 15 is located right below thesupporting layer recess 612. The supporting layer recess 612 iscommunicated with the substrate recess 15, and the supporting layerrecess 612 and the substrate recess 15 have a boundary 103 therebetweenand the boundary 103 is the extended from the top surface of thecompound semiconductor epitaxial substrate 10. The bulk acousticresonator structure 60 is formed on the supporting layer 61, wherein thebulk acoustic resonator structure 60 includes: a bottom electrode 601, adielectric layer 602 and a top electrode 603. The bottom electrode 601is formed on one end of the supporting layer 61, where the bottomelectrode 601 is formed on and at least extended along the supportinglayer mesa 611. The dielectric layer 602 is formed at least on thebottom electrode 601 above the supporting layer mesa 611. In theembodiment of FIG. 1, the dielectric layer 602 is formed on both thebottom electrode 601 and the supporting layer 61, and the dielectriclayer 602 is also formed on the bottom electrode 601 above thesupporting layer mesa 611. Please also refer to FIG. 1A, which shows thecross-sectional view of another embodiment of the integrated structureof power amplifier and acoustic wave device of the present invention.The main structure in FIG. 1A is basically the same as the structureshown in FIG. 1, except that the dielectric layer 602 is formed on thebottom electrode 601 above the supporting layer mesa 611 and also formedon a small part of the supporting layer 61 above the supporting layermesa 611. The top electrode 603 is formed on the other end with respectto the bottom electrode 601, where the top electrode 603 is formed onthe dielectric layer 602 or formed on both the dielectric layer 602 andthe supporting layer 61, and the top electrode 603 is formed on and atleast extended along the dielectric layer 602 above the supporting layermesa 611. In the embodiment of FIG. 1, the top electrode 603 is formedon the dielectric layer 602, while in embodiment of FIG. 1A, the topelectrode 603 is formed on both the dielectric layer 602 and thesupporting layer 61. The top electrode 603 and the bottom electrode 601are not electrically connected. The gap between the supporting layermesa 611 and the bottom of the substrate recess 15 is increased by thecommunication of the supporting layer recess 612 and the substraterecess 15, so as to avoid the contact of the supporting layer mesa 611and the bottom of the substrate recess 15 when the film bulk acousticresonator 51 is affected by stress such that the supporting layer mesa611 is bended downwardly.

In an embodiment, the integrated structure 1 of power amplifier 20 andacoustic wave device 50 is not limited to integrating one single poweramplifier 20 and one single acoustic wave device 50. In anotherembodiment, the integrated structure 1 of power amplifier 20 andacoustic wave device 50 may integrates one single power amplifier 20 andplural acoustic wave devices 50, plural power amplifiers 20 and onesingle acoustic wave device 50 or plural power amplifiers 20 and pluralacoustic wave devices 50.

In an embodiment, the integrated structure 1 of power amplifier 20 andacoustic wave device 50 may also integrate other components, such asmetal-insulator-metal capacitor, resistor, inductor or diode, on thesame the compound semiconductor epitaxial substrate 10, wherein thecomponents may be directly or indirectly electrically connected. Inanother embodiment, the power amplifier 20 and the acoustic wave device50 may be directly electrically connected. In other embodiment, thepower amplifier 20 may be indirectly electrically connected with theacoustic wave device 50 through other component(s) on the integratedstructure.

In an embodiment, the application of the acoustic wave device 50 may bea filter. Usually plural acoustic wave devices 50 are in series and/orin parallel in the combination of circuit to form a filter which mayfilter the signal. In another embodiment, the signal may flow into thefilter formed by the acoustic wave devices 50 to be filtered, and thenthe filtered signal flows into the power amplifier 20 to be amplified.In other embodiment, the signal may flow into the power amplifier 20 tobe amplified, and then the amplified signal flows into the filter formedby the acoustic wave devices 50 to be filtered. In one anotherembodiment, the integrated structure may integrate one power amplifier20 and two filters formed by acoustic wave devices 50. The signal mayfirstly flow into the first filter formed by acoustic wave devices 50 tobe filtered, and then flow into the power amplifier 20 to be amplified,and finally flow into the second filter formed by acoustic wave devices50 to be filtered.

In one embodiment, the application of the acoustic wave device 50 may bea mass sensing device, a biomedical sensing device, an UV sensingdevice, a pressure sensing device or a temperature sensing device.

In an embodiment, the compound semiconductor substrate 12 may be made ofGaAs, SiC, InP, GaN, AlN or Sapphire.

In an embodiment, the function of the supporting layer 61 may be thesupporting for the film bulk acoustic resonator 51 for preventing thefilm bulk acoustic resonator 51 from collapsing. The supporting layer 61also may be the seed layer for the bottom electrode 601 and thedielectric layer 602 for improving the crystalline quality. In anembodiment, the supporting layer 61 is made of SiN_(x) or AlN. Thesupporting layer 61 is formed on the epitaxial structure 13 by molecularbeam epitaxy (MBE), sputtering or chemical vapor deposition (CVD).

In an embodiment, the bottom electrode 601 is needed to have a lowerroughness and resistivity for benefit the preferable crystal growthaxis. In an embodiment, the bottom electrode 601 is made of Mo, Pt, Al,Au, W or Ru. The bottom electrode 601 is formed on the supporting layer61 by evaporation or sputtering.

In an embodiment, the dielectric layer 602 is made of AlN,monocrystalline SiO₂, ZnO, HfO₂, barium strontium titanate (BST) or leadzirconate titanate (PZT), and is formed on the bottom electrode 601 orformed on both the electrode 601 and the supporting layer 61 byepitaxial growth or sputtering. The selection of the materials of thedielectric layer 602 is associated with the application. AlN is a highacoustic wave velocity material (12000 m/s) and is suitable for highfrequency application, and after the formation of the micro structure ofthe material, it has good physical and chemical stability and itsproperties are not easily to be influenced by the circumstance. ZnO maybe formed under lower temperature and it has an acoustic wave velocity6000 m/s. Its electromechanical coupling coefficient is higher (8.5%)and it is suitable for the application of broadband filter. However whenforming ZnO, the concentration of oxygen vacancies in ZnO is not easilycontrolled, yet it is easily influenced by the humidity and oxygen ofthe circumstance. Both barium strontium titanate (BST) and leadzirconate titanate (PZT) are ferroelectric materials. Their dielectricconstant may vary under external electric field. Hence, they aresuitable for the application of acoustic wave device with tunablefrequency within dozen MHz range of frequencies. Both barium strontiumtitanate (BST) and lead zirconate titanate (PZT) need to be polarizedunder high voltage electric field in order to obtain their piezoelectriccharacteristics. Lead zirconate titanate (PZT) has higherelectromechanical coupling coefficient, however it contains lead.

In an embodiment, the top electrode 603 is needed to have a lowerresistivity for reducing power loss so as to reduce the insertion loss.In an embodiment, the top electrode 603 may be made of Mo, Pt, Al, Au, Wor Ru. The top electrode 603 is formed on the dielectric layer 602 or isformed on both the dielectric layer 602 and the supporting layer 61 byevaporation or sputtering.

In an embodiment, the bottom electrode 601 is made of Mo or Pt, whilethe dielectric layer 602 is made of AlN. The Mo of the bottom electrode601 may be etched by Lithography and Lift-off process. And the AlN ofthe dielectric layer 602 may be etched by inductively coupled plasma(ICP) process with CF₄ plasma.

In an embodiment, the depth of the substrate recess 15 is between 50 nmand 10000 nm.

In an embodiment, the depth of the supporting layer recess 612 isbetween 10 nm and 3500 nm. In another embodiment, the optimized depth ofthe supporting layer recess 612 is between 10 nm and 1500 nm.

Please refer to FIG. 1B, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 1B isbasically the same as the structure shown in FIG. 1, except that thefilm bulk acoustic resonator 51 further comprises at least one etchingrecess 62. The cross-sectional direction of FIG. 1B is orthogonal tothat of FIG. 1. And there is only the acoustic wave device 50 at theposition of the cross-sectional direction of FIG. 1B, hence there is nopower amplifier 20 shown in FIG. 1B. One end of the at least one etchingrecess 62 is communicated with the supporting layer recess 612, theother end of the at least one etching recess 62 penetrates thesupporting layer 61 or penetrates both the supporting layer 61 and thebulk acoustic resonator structure 60 such that the at least one etchingrecess 62 is communicated with the outside, and thereby the supportinglayer recess 612 is communicated with the outside.

Please refer to the embodiment of FIGS. 1 and 1B, the present inventionprovides a fabrication method for integrated structure of poweramplifier and acoustic wave device. The fabrication method for theembodiment of FIGS. 1 and 1B comprises following steps of: Step A1:forming an epitaxial structure 13 on a compound semiconductor substrate12 to form a compound semiconductor epitaxial substrate 10; Step A2:forming a power amplifier upper structure 21 on a top-side of a leftpart 101 of the compound semiconductor epitaxial substrate 10 to form apower amplifier 20; and Step A3: forming a film bulk acoustic resonator51 on the top-side of a right part 102 of the compound semiconductorepitaxial substrate 10 to form an acoustic wave device 50. Theintegrated structure 1 of the power amplifier 20 and the acoustic wavedevice 50 on the same the compound semiconductor epitaxial substrate 10is capable of reducing the component size, optimizing the impedancematching, and reducing the signal loss between the power amplifier 20and the acoustic wave device 50. Step A3 includes following steps of:Step A31: (Please referring to FIG. 1C) forming a top sacrificial layer63 on the compound semiconductor epitaxial substrate 10; Step A32:defining a top sacrificial layer etching area, and etching to remove thetop sacrificial layer 63 within the top sacrificial layer etching areato form a top sacrificial layer mesa 632, such that the compoundsemiconductor epitaxial substrate 10 within the top sacrificial layeretching area is exposed; Step A33: (Please referring to FIG. 1D) forminga supporting layer 61 on the top sacrificial layer 63 and the compoundsemiconductor epitaxial substrate 10, wherein the supporting layer 61has a supporting layer mesa 611 right above the top sacrificial layermesa 632; Step A34: forming a bulk acoustic resonator structure 60 onthe supporting layer 61 (Please referring to FIGS. 1E and 1F, whereinthe cross-sectional direction of FIG. 1F is orthogonal to that of FIG.1E, and there is only the acoustic wave device 50 at the position of thecross-sectional direction of FIG. 1F, hence there is no power amplifier20 shown in FIG. 1F), which includes following steps of: Step A341:forming a bottom electrode 601 on one end of the supporting layer 61,where the bottom electrode 601 is formed on and at least extended alongthe supporting layer mesa 611; Step A342: forming a dielectric layer602, wherein the dielectric layer 602 is formed at least on the bottomelectrode 601 above the supporting layer mesa 611; and Step A343:forming a top electrode 603, wherein the top electrode 603 is formed onthe other end with respect to the bottom electrode 601, where the topelectrode 603 is formed on the dielectric layer 602 or formed on boththe dielectric layer 602 and the supporting layer 61, and the topelectrode 603 is formed on and at least extended along the dielectriclayer 602 above the supporting layer mesa 611; Step A35: (Pleasereferring to FIG. 1G) defining at least one recess etching area, andetching to remove the supporting layer 61 within the at least one recessetching area or etching to remove the supporting layer 61 and the bulkacoustic resonator structure 60 within the at least one recess etchingarea such that the etching stops at the top sacrificial layer mesa 632and/or the compound semiconductor epitaxial substrate 10 to form atleast one etching recess 62, thereby part of the top sacrificial layermesa 632 is exposed; Step A36: (Please referring to FIG. 1H) etching toremove the top sacrificial layer mesa 632 to form a supporting layerrecess 612, wherein at least one top sacrificial layer etching solutioncontacts with the top sacrificial layer mesa 632 via the at least oneetching recess 62 and etches to remove the top sacrificial layer mesa632, thereby the top and the bottom of the supporting layer recess 612are the supporting layer 61 and the compound semiconductor epitaxialsubstrate 10 respectively; and Step A37: etching to remove part of thecompound semiconductor epitaxial substrate 10 below the supporting layerrecess 612 to form a substrate recess 15 (Please referring to FIGS. 1and 1B, wherein the cross-sectional direction of FIG. 1B is orthogonalto that of FIG. 1, and there is only the acoustic wave device 50 at theposition of the cross-sectional direction of FIG. 1B, hence there is nopower amplifier 20 shown in FIG. 1B), wherein the bottom of thesubstrate recess 15 is the compound semiconductor epitaxial substrate10, wherein at least one substrate recess etching solution contacts withthe top surface of the compound semiconductor epitaxial substrate 10 viathe at least one etching recess 62 and the supporting layer recess 612,the at least one substrate recess etching solution is uniformlydistributed on the top surface of the compound semiconductor epitaxialsubstrate 10 through the supporting layer recess 612 so as to uniformlyetch part of the compound semiconductor epitaxial substrate 10 below thesupporting layer recess 612 to form the substrate recess 15, and therebyprevents the side etching phenomenon during the etching, wherein thesupporting layer recess 612 is communicated with the substrate recess15, and the supporting layer recess 612 and the substrate recess 15 havea boundary 103 therebetween and the boundary 103 is the extended fromthe top surface of the compound semiconductor epitaxial substrate 10,wherein the gap between the supporting layer mesa 611 and the bottom ofthe substrate recess 15 is increased by the communication of thesupporting layer recess 612 and the substrate recess 15, so as to avoidthe contact of the supporting layer mesa 611 and the bottom of thesubstrate recess 15 when the film bulk acoustic resonator 51 is affectedby stress such that the supporting layer mesa 611 is bended downwardly.

Please refer to FIG. 1I, which shows the partial enlargedcross-sectional view of an embodiment of the integrated structure ofpower amplifier and acoustic wave device of the present invention. Inthe embodiment of FIG. 1I, the supporting layer recess 612 has anopening smaller than that of the substrate recess 15. Please refer toFIG. 1J, which shows the partial enlarged cross-sectional view ofanother embodiment of the integrated structure of power amplifier andacoustic wave device of the present invention. In the embodiment of FIG.1J, the supporting layer recess 612 has an opening almost equal to thatof the substrate recess 15.

Please refer to FIGS. 1K, 1L, 1M and 1N, which show the top views of therelative position of the etching recess and the supporting layer mesa inthe embodiments of the integrated structure of power amplifier andacoustic wave device of the present invention. In the embodiment of FIG.1K, the integrated structure 1 of power amplifier 20 and acoustic wavedevice 50 has two etching recess 62 with long strip opening. The twoetching recesses 62 are located on two opposite sides of the supportinglayer mesa 611 respectively. And the etching recesses 62 penetrate thesupporting layer 61 (not shown in FIG. 1K), and thereby the supportinglayer recess 612 (not shown in FIG. 1K) is communicated with theoutside. In the embodiment of FIG. 1L, the integrated structure 1 ofpower amplifier 20 and acoustic wave device 50 has two etching recess 62with long strip opening. The two etching recesses 62 are located on twoopposite sides of the supporting layer mesa 611 respectively. (part ofthe etching recesses 62 are within the supporting layer mesa 611, therest part of the etching recesses 62 are outside the supporting layermesa 611) And the etching recesses 62 penetrate the supporting layer 61(not shown in FIG. 1L) and the dielectric layer 602. In the embodimentof FIG. 1M, the integrated structure 1 of power amplifier 20 andacoustic wave device 50 has two etching recess 62 with long stripopening. The two etching recesses 62 are located respectively on twoopposite sides of the supporting layer mesa 611 within the supportinglayer mesa 611. And the etching recesses 62 penetrate the supportinglayer 61 (not shown in FIG. 1M), the bottom electrode 601, thedielectric layer 602 and the top electrode 603. In the embodiment ofFIG. 1N, the integrated structure 1 of power amplifier 20 and acousticwave device 50 has four etching recess 62 with square opening. The fouretching recesses 62 are located on four corners of the supporting layermesa 611 respectively. And the etching recesses 62 penetrate thesupporting layer 61 (not shown in FIG. 1N). The amount of the etchingrecesses 62 is not limited to one, two, three, four or more. The etchingrecesses 62 may locate on other position and should not be limited byFIG. 1K, 1L, 1M or 1N.

In one embodiment, the power amplifier 20 may be a heterojunctionbipolar transistor (HBT). In another embodiment, the power amplifier 20may be a field effect transistor (FET), a high electron mobilitytransistor (HEMT) or a pseudomorphic high electron mobility transistor(pHEMT). In an embodiment, the power amplifier 20 may be any other typeof amplifier which may be formed on the compound semiconductor substrate12.

Please refer to FIG. 2, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 2 isbasically the same as the structure shown in FIG. 1, except that thepower amplifier 20 is a heterojunction bipolar transistor 30 (HBT). Theepitaxial structure 13 includes: a subcollector layer 31 and a collectorlayer 33. The subcollector layer 31 formed on the compound semiconductorsubstrate 12; the collector layer 33 formed on the subcollector layer31. The left part 101 of the compound semiconductor epitaxial substrate10 further comprises a collector recess 331, and the bottom of thecollector recess 331 is the subcollector layer 31. The power amplifierupper structure 21 includes: a base layer 34, an emitter ledge layer 35,an emitter layer 36, a base electrode 38, an emitter electrode 39 and acollector electrode 37. The base layer 34 is formed on the collectorlayer 33; the emitter ledge layer 35 is formed on the base layer 34; theemitter layer 36 is formed on the emitter ledge layer 35; the baseelectrode 38 is formed on the emitter ledge layer 35; the emitterelectrode 39 is formed on the emitter layer 36; the collector electrode37 is formed on the subcollector layer 31 within the collector recess331. The left part 101 of the compound semiconductor epitaxial substrate10 includes: the compound semiconductor substrate 12, the subcollectorlayer 31, the collector layer 33 and the collector recess 331. The leftpart 101 of the compound semiconductor epitaxial substrate 10 and thepower amplifier upper structure 21 form the heterojunction bipolartransistor 30. The acoustic wave device 50 in FIG. 2 is basically thesame as the acoustic wave device 50 in FIG. 1. The substrate recess 15of the right part 102 of the compound semiconductor epitaxial substrate10 is peripherally surrounded by the collector layer 33, and the bottomof the substrate recess 15 is the subcollector layer 31. The right part102 of the compound semiconductor epitaxial substrate 10 and the filmbulk acoustic resonator 51 form the acoustic wave device 50.

In one embodiment, the collector layer 33 is made of GaAs. The thicknessof the collector layer 33 is between 500 nm and 3000 nm.

In another embodiment, the base layer 34 is made of GaAs. The thicknessof the base layer 34 is between 60 nm and 100 nm.

In one embodiment, the subcollector layer 31 is made of GaAs and isformed on the compound semiconductor substrate 12 by epitaxial growth.

Please refer to FIG. 2A, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 2A isbasically the same as the structure shown in FIG. 2, except that thebase electrode 38 is formed on the base layer 34. In one otherembodiment, the base electrode 38 may be formed on both the base layer34 and the emitter ledge layer 35. In other embodiments having basicallythe same structure as the embodiment in FIG. 2, the base electrode 38may be formed on the base layer 34 and/or the emitter ledge layer 35.

Please refer to FIG. 2B, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 2B isbasically the same as the structure shown in FIG. 2, except that theheterojunction bipolar transistor 30 further comprises the supportinglayer 61. The supporting layer 61 plays a role of protection, and mayprevent the heterojunction bipolar transistor 30 from oxidation orcorrosion. In other embodiments having basically the same structure asthe embodiment in FIG. 2, the power amplifier 20 may also include thesupporting layer 61.

Please refer to FIG. 2C, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 2C isbasically the same as the structure shown in FIG. 2, except that thefilm bulk acoustic resonator 51 further comprises at least one etchingrecess 62. The cross-sectional direction of FIG. 2C is orthogonal tothat of FIG. 2. And there is only the acoustic wave device 50 at theposition of the cross-sectional direction of FIG. 2C, hence there is nopower amplifier 20 shown in FIG. 2C. One end of the at least one etchingrecess 62 is communicated with the supporting layer recess 612, theother end of the at least one etching recess 62 penetrates thesupporting layer 61 or penetrates both the supporting layer 61 and thebulk acoustic resonator structure 60 such that the at least one etchingrecess 62 is communicated with the outside, and thereby the supportinglayer recess 612 is communicated with the outside. The feature of the atleast one etching recess 62 of the embodiment in FIG. 2C is basicallythe same as that of the embodiment in FIG. 1B. The power amplifier 20may also include the supporting layer 61, or may choose not to includethe supporting layer 61.

Please refer to FIG. 2D, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 2D isbasically the same as the structure shown in FIG. 2B, except that theepitaxial structure 13 further comprises an etching stop layer 32;wherein the etching stop layer 32 is formed on the subcollector layer31; and the collector layer 33 is formed on the etching stop layer 32.The bottom of the collector recess 331 is the subcollector layer 31, thecollector electrode 37 is formed on the subcollector layer 31 within thecollector recess 331. The substrate recess 15 is peripherally surroundedby the collector layer 33 and the etching stop layer 32, and the bottomof the substrate recess 15 is the subcollector layer 31. The poweramplifier 20 may also include the supporting layer 61, or may choose notto include the supporting layer 61.

In an embodiment, the etching stop layer 32 is made of InGaP. In oneembodiment, the thickness of the etching stop layer 32 is between 5 nmand 1000 nm. In another embodiment, the optimized thickness of theetching stop layer 32 is 20 nm.

Please refer to FIG. 2E, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 2E isbasically the same as the structure shown in FIG. 2D, except that thefilm bulk acoustic resonator 51 further comprises at least one etchingrecess 62. The cross-sectional direction of FIG. 2E is orthogonal tothat of FIG. 2D. And there is only the acoustic wave device 50 at theposition of the cross-sectional direction of FIG. 2E, hence there is nopower amplifier 20 shown in FIG. 2E. One end of the at least one etchingrecess 62 is communicated with the supporting layer recess 612, theother end of the at least one etching recess 62 penetrates thesupporting layer 61 or penetrates both the supporting layer 61 and thebulk acoustic resonator structure 60 such that the at least one etchingrecess 62 is communicated with the outside, and thereby the supportinglayer recess 612 is communicated with the outside. The feature of the atleast one etching recess 62 of the embodiment in FIG. 2E is basicallythe same as that of the embodiment in FIG. 1B. The power amplifier 20may also include the supporting layer 61, or may choose not to includethe supporting layer 61.

Please refer to FIGS. 2B and 2C. The cross-sectional direction of FIG.2C is orthogonal to that of FIG. 2B. And there is only the acoustic wavedevice 50 at the position of the cross-sectional direction of FIG. 2C,hence there is no power amplifier 20 shown in FIG. 2C. The presentinvention provides a fabrication method for integrated structure ofpower amplifier and acoustic wave device. The fabrication method for theembodiment of FIGS. 2B and 2C comprises following steps of: Step B1:forming an epitaxial structure 13 on a compound semiconductor substrate12 to form a compound semiconductor epitaxial substrate 10; Step B2:forming a power amplifier upper structure 21 on a top-side of a leftpart 101 of the compound semiconductor epitaxial substrate 10 to form apower amplifier 20, wherein the power amplifier 20 is a heterojunctionbipolar transistor 30 (HBT); and Step B3: forming a film bulk acousticresonator 51 on the top-side of a right part 102 of the compoundsemiconductor epitaxial substrate 10 to form an acoustic wave device 50;wherein, the integrated structure 1 of the power amplifier 20 and theacoustic wave device 50 on the same the compound semiconductor epitaxialsubstrate 10 is capable of reducing the component size, optimizing theimpedance matching, and reducing the signal loss between the poweramplifier 20 and the acoustic wave device 50. In this embodiment, StepB1 further includes following steps of: Step B11: (Please referring toFIG. 2F) forming a subcollector layer 31 on the compound semiconductorsubstrate 12; and Step B12: forming a collector layer 33 on thesubcollector layer 31. Step B2 and Step B3 include following steps of:Step B41: (Please referring to FIG. 2H) forming a base layer 34 on thecollector layer 33; Step B42: forming an emitter ledge layer 35 on thebase layer 34; Step B43: forming an emitter layer 36 on the emitterledge layer 35; Step B44: (Please referring to FIG. 2I) defining anemitter layer etching area, and etching to remove the emitter layer 36within the emitter layer etching area; Step B45: forming a baseelectrode 38 on the emitter ledge layer 35; Step B46: (Please referringto FIG. 2J) defining an emitter ledge layer etching area, and etching toremove the emitter ledge layer 35 within the emitter ledge layer etchingarea; Step B47: defining a base layer etching area, and etching toremove the base layer 34 within the base layer etching area; Step B48:(Please referring to FIG. 2L) forming a top sacrificial layer 63 on thecompound semiconductor epitaxial substrate 10 (the collector layer 33);Step B49: defining a top sacrificial layer etching area, and etching toremove the top sacrificial layer 63 within the top sacrificial layeretching area to form a top sacrificial layer mesa 632, such that thecompound semiconductor epitaxial substrate 10 (the collector layer 33)within the top sacrificial layer etching area is exposed; Step B50:(Please referring to FIGS. 2M and 2N) forming a supporting layer 61 onthe top sacrificial layer 63 and the compound semiconductor epitaxialsubstrate 10 (the collector layer 33), wherein the supporting layer 61has a supporting layer mesa 611 right above the top sacrificial layermesa 632; wherein the supporting layer 61 may also be formed on the baselayer 34, the emitter ledge layer 35, the emitter layer 36 and the baseelectrode 38, and the supporting layer 61 may play a role of protection;Step B51: forming a bulk acoustic resonator structure 60 on thesupporting layer 61, which includes following steps of: Step B511:(Please referring to FIG. 20) forming a bottom electrode 601 on one endof the supporting layer 61, where the bottom electrode 601 is formed onand at least extended along the supporting layer mesa 611; and formingan emitter electrode 39 on the emitter layer 36 (the emitter electrode39 may choose to be formed on the emitter layer 36 through other step);Step B512: (Please referring to FIG. 2P) forming a dielectric layer 602,wherein the dielectric layer 602 is formed at least on the bottomelectrode 601 above the supporting layer mesa 611; and Step B513:(Please referring to FIG. 2Q) forming a top electrode 603, wherein thetop electrode 603 is formed on the other end with respect to the bottomelectrode 601, where the top electrode 603 is formed on the dielectriclayer 602 or formed on both the dielectric layer 602 and the supportinglayer 61, and the top electrode 603 is formed on and at least extendedalong the dielectric layer 602 above the supporting layer mesa 611; StepB52: defining at least one recess etching area, and etching to removethe supporting layer 61 within the at least one recess etching area oretching to remove the supporting layer 61 and the bulk acousticresonator structure 60 within the at least one recess etching area suchthat the etching stops at the top sacrificial layer mesa 632 and/or thecompound semiconductor epitaxial substrate 10 (the collector layer 33)to form at least one etching recess 62, thereby part of the topsacrificial layer mesa 632 is exposed (Please referring to FIGS. 2R and2S, wherein the cross-sectional direction of FIG. 2S is orthogonal tothat of FIG. 2R, and there is only the acoustic wave device 50 at theposition of the cross-sectional direction of FIG. 2S, hence there is nopower amplifier 20 shown in FIG. 2S); Step B53: etching to remove thetop sacrificial layer mesa 632 to form a supporting layer recess 612,wherein at least one top sacrificial layer etching solution contactswith the top sacrificial layer mesa 632 via the at least one etchingrecess 62 and etches to remove the top sacrificial layer mesa 632,thereby the top and the bottom of the supporting layer recess 612 arethe supporting layer 61 and the compound semiconductor epitaxialsubstrate 10 (the collector layer 33) respectively (Please referring toFIGS. 2T and 2U, wherein the cross-sectional direction of FIG. 2U isorthogonal to that of FIG. 2T, and there is only the acoustic wavedevice 50 at the position of the cross-sectional direction of FIG. 2U,hence there is no power amplifier 20 shown in FIG. 2U); Step B54:defining a collector electrode etching area, and etching to remove thecollector layer 33 within the collector electrode etching area such thatthe etching stops at the subcollector layer 31 to form a collectorrecess 331 (Please referring to FIGS. 2V and 2W, wherein thecross-sectional direction of FIG. 2W is orthogonal to that of FIG. 2V,and there is only the acoustic wave device 50 at the position of thecross-sectional direction of FIG. 2W, hence there is no power amplifier20 shown in FIG. 2W), thereby the subcollector layer 31 within thecollector recess 331 is exposed; and etching to remove part of thecompound semiconductor epitaxial substrate 10 below the supporting layerrecess 612 to form a substrate recess 15, wherein the bottom of thesubstrate recess 15 is the compound semiconductor epitaxial substrate 10(the subcollector layer 31), wherein at least one substrate recessetching solution contacts with the top surface of the compoundsemiconductor epitaxial substrate 10 (the collector layer 33) via the atleast one etching recess 62 and the supporting layer recess 612, the atleast one substrate recess etching solution is uniformly distributed onthe top surface of the compound semiconductor epitaxial substrate 10(the collector layer 33) through the supporting layer recess 612 so asto uniformly etch part of the compound semiconductor epitaxial substrate10 below the supporting layer recess 612 to form the substrate recess15, and thereby prevents the side etching phenomenon during the etching,wherein the supporting layer recess 612 is communicated with thesubstrate recess 15, and the supporting layer recess 612 and thesubstrate recess 15 have a boundary 103 therebetween and the boundary103 is the extended from the top surface of the compound semiconductorepitaxial substrate 10, wherein the gap between the supporting layermesa 611 and the bottom of the substrate recess 15 is increased by thecommunication of the supporting layer recess 612 and the substraterecess 15, so as to avoid the contact of the supporting layer mesa 611and the bottom of the substrate recess 15 when the film bulk acousticresonator 51 is affected by stress such that the supporting layer mesa611 is bended downwardly; and Step B55: forming a collector electrode 37on the subcollector layer 31 within the collector recess 331 (Pleasereferring to FIGS. 2B and 2C, wherein the cross-sectional direction ofFIG. 2C is orthogonal to that of FIG. 2B, and there is only the acousticwave device 50 at the position of the cross-sectional direction of FIG.2C, hence there is no power amplifier 20 shown in FIG. 2C); thereby theleft part 101 of the compound semiconductor epitaxial substrate 10includes: the compound semiconductor substrate 12, the subcollectorlayer 31, the collector layer 33 and the collector recess 331; the poweramplifier upper structure 21 includes: the base layer 34, the emitterledge layer 35, the emitter layer 36, the base electrode 38, the emitterelectrode 39 and the collector electrode 37; wherein the left part 101of the compound semiconductor epitaxial substrate 10 and the poweramplifier upper structure 21 form the heterojunction bipolar transistor30; wherein the substrate recess 15 is peripherally surrounded by thecollector layer 33, and the bottom of the substrate recess 15 is thesubcollector layer 31.

Step B44, Step B45 and Step B46 may be substituted by Step B441, StepB451, Step B461 and Step B462. These steps are as follows: Step B441:(Please referring to FIG. 2K) defining an emitter layer etching area,and etching to remove the emitter layer 36 within the emitter layeretching area; Step B451: defining an emitter ledge layer etching area,and etching to remove the emitter ledge layer 35 within the emitterledge layer etching area; Step B461: forming a base electrode 38 on thebase layer 34; Step B462: defining a base layer etching area, andetching to remove the base layer 34 within the base layer etching area.

Please refer to FIGS. 2G 2D and 2E, in which FIG. 2G shows thecross-sectional schematic of the steps of the fabrication method for theembodiment of FIGS. 2D and 2E of the integrated structure of poweramplifier and acoustic wave device of the present invention. The stepsof the fabrication method for the embodiment of FIGS. 2D and 2E arebasically the same as the fabrication method steps for the embodiment ofFIGS. 2B and 2C, except that Step B1 further comprises Step B115:forming an etching stop layer 32 on the subcollector layer 31; and StepB545: etching to remove the etching stop layer 32 within the collectorelectrode etching area such that the etching stops at the subcollectorlayer 31 to form the collector recess 331, and thereby the subcollectorlayer 31 within the collector recess 331 is exposed. Step B115 isbetween Step B11 and Step B12, i.e. first, forming the subcollectorlayer 31 on the compound semiconductor substrate 12, then forming theetching stop layer 32 on the subcollector layer 31, and then forming thecollector layer 33 on the etching stop layer 32, such that the epitaxialstructure 13 includes: the subcollector layer 31, the etching stop layer32 and the collector layer 33. Step B545 is between Step B54 and StepB55. Step B545 may also includes a step of etching to remove the etchingstop layer 32 below the bottom of the substrate recess 15, such that thesubstrate recess 15 is peripherally surrounded by the collector layer 33and the etching stop layer 32, and the bottom of the substrate recess 15is the subcollector layer 31. The collector electrode 37 is formed onthe subcollector layer 31 within the collector recess 331. Thereby theleft part 101 of the compound semiconductor epitaxial substrate 10includes: the compound semiconductor substrate 12, the subcollectorlayer 31, the etching stop layer 32, the collector layer 33 and thecollector recess 331. The power amplifier upper structure 21 includes:the base layer 34, the emitter ledge layer 35, the emitter layer 36, thebase electrode 38, the emitter electrode 39 and the collector electrode37. The left part 101 of the compound semiconductor epitaxial substrate10 and the power amplifier upper structure 21 form the heterojunctionbipolar transistor 30.

In an embodiment, the top sacrificial layer 63 is made of AlAs or TiW.

In an embodiment, the TiW of the top sacrificial layer 63 may be formedby sputtering on the epitaxial structure 13 (the collector layer 33).TiW may be etched by H₂O₂.

In an embodiment, the AlAs of the top sacrificial layer 63 may be formedby molecular beam epitaxy (MBE) or metal organic chemical vapordeposition (MOCVD) on the epitaxial structure 13 (the collector layer33).

In an embodiment, the thickness of the top sacrificial layer 63 isbetween 10 nm and 3500 nm. In another embodiment, the optimizedthickness of the top sacrificial layer 63 is between 10 nm and 1500 nm.

Please refer to FIG. 3, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 3 isbasically the same as the structure shown in FIG. 1, except that thepower amplifier 20 is a pseudomorphic high electron mobility transistor40 (pHEMT). The epitaxial structure 13 includes: a buffer layer 41, achannel layer 42, a Schottky layer 43 and a cap layer 44; wherein thebuffer layer 41 is formed on the compound semiconductor substrate 12;the channel layer 42 is formed on the buffer layer 41; the Schottkylayer 43 is formed on the channel layer 42; the cap layer 44 is formedon the Schottky layer 43. The left part 101 of the compoundsemiconductor epitaxial substrate 10 further comprises a gate recess451; the bottom of the gate recess 451 is the Schottky layer 43; whereinthe power amplifier upper structure 21 includes: a drain electrode 47, asource electrode 46 and a gate electrode 45; wherein the drain electrode47 is formed on one end of the cap layer 44; the source electrode 46 isformed on the other end of the cap layer 44, wherein the gate recess 451is located between the drain electrode 47 and the source electrode 46;the gate electrode 45 is formed on the Schottky layer 43 within the gaterecess 451; thereby the left part 101 of the compound semiconductorepitaxial substrate 10 includes: the compound semiconductor substrate12, the buffer layer 41, the channel layer 42, the Schottky layer 43,the cap layer 44 and the gate recess 451; wherein the left part 101 ofthe compound semiconductor epitaxial substrate 10 and the poweramplifier upper structure 21 form the pseudomorphic high electronmobility transistor 40. The acoustic wave device 50 in FIG. 3 isbasically the same as the acoustic wave device 50 in FIG. 1. Thesubstrate recess 15 of the right part 102 of the compound semiconductorepitaxial substrate 10 is peripherally surrounded by the buffer layer41, the channel layer 42, the Schottky layer 43 and the cap layer 44;and the bottom of the substrate recess 15 is the buffer layer 41. Theright part 102 of the compound semiconductor epitaxial substrate 10 andthe film bulk acoustic resonator 51 form the acoustic wave device 50.

In an embodiment, the buffer layer 41 is made of GaAs, SiO₂ or GaN andis formed on the compound semiconductor substrate 12 by epitaxialgrowth.

In an embodiment, the compound semiconductor substrate 12 is made ofGaAs, while the buffer layer 41 is preferable to be made of GaAs. Inanother embodiment, the compound semiconductor substrate 12 is made ofSapphire, while the buffer layer 41 is preferable to be made of GaN.

Please refer to FIG. 3A, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 3A isbasically the same as the structure shown in FIG. 3, except that thepseudomorphic high electron mobility transistor 40 further comprises thesupporting layer 61. The supporting layer 61 plays a role of protection,and may prevent the pseudomorphic high electron mobility transistor 40from oxidation or corrosion. In other embodiments having basically thesame structure as the embodiment in FIG. 3, the power amplifier 20 mayalso include the supporting layer 61.

Please refer to FIG. 3B, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 3B isbasically the same as the structure shown in FIG. 3, except that thesubstrate recess 15 of the right part 102 of the compound semiconductorepitaxial substrate 10 is peripherally surrounded by the channel layer42, the Schottky layer 43 and the cap layer 44, and the bottom of thesubstrate recess 15 is the buffer layer 41. The power amplifier 20 mayalso include the supporting layer 61, or may choose not to include thesupporting layer 61.

Please refer to FIG. 3C, which shows the cross-sectional view of anotherembodiment of the integrated structure of power amplifier and acousticwave device of the present invention. The main structure in FIG. 3C isbasically the same as the structure shown in FIG. 3, except that thefilm bulk acoustic resonator 51 further comprises at least one etchingrecess 62. The cross-sectional direction of FIG. 3C is orthogonal tothat of FIG. 3. And there is only the acoustic wave device 50 at theposition of the cross-sectional direction of FIG. 3C, hence there is nopower amplifier 20 shown in FIG. 3C. One end of the at least one etchingrecess 62 is communicated with the supporting layer recess 612, theother end of the at least one etching recess 62 penetrates thesupporting layer 61 or penetrates both the supporting layer 61 and thebulk acoustic resonator structure 60 such that the at least one etchingrecess 62 is communicated with the outside, and thereby the supportinglayer recess 612 is communicated with the outside. The feature of the atleast one etching recess 62 of the embodiment in FIG. 3C is basicallythe same as that of the embodiment in FIG. 1B. The power amplifier 20may also include the supporting layer 61, or may choose not to includethe supporting layer 61.

Please refer to FIGS. 3A and 3C. The cross-sectional direction of FIG.3C is orthogonal to that of FIG. 3A. And there is only the acoustic wavedevice 50 at the position of the cross-sectional direction of FIG. 3C,hence there is no power amplifier 20 shown in FIG. 3C. The presentinvention provides a fabrication method for integrated structure ofpower amplifier and acoustic wave device. The fabrication method for theembodiment of FIGS. 3A and 3C comprises following steps of: Step C1:forming an epitaxial structure 13 on a compound semiconductor substrate12 to form a compound semiconductor epitaxial substrate 10; Step C2:forming a power amplifier upper structure 21 on a top-side of a leftpart 101 of the compound semiconductor epitaxial substrate 10 to form apower amplifier 20, wherein the power amplifier 20 is a pseudomorphichigh electron mobility transistor 40; and Step C3: forming a film bulkacoustic resonator 51 on the top-side of a right part 102 of thecompound semiconductor epitaxial substrate 10 to form an acoustic wavedevice 50; wherein, the integrated structure 1 of the power amplifier 20and the acoustic wave device 50 on the same the compound semiconductorepitaxial substrate 10 is capable of reducing the component size,optimizing the impedance matching, and reducing the signal loss betweenthe power amplifier 20 and the acoustic wave device 50. Step C1 includesfollowing steps of: Step C11: (Please referring to FIG. 3D) forming abuffer layer 41 on the compound semiconductor substrate 12; Step C12:forming a channel layer 42 on the buffer layer 41; Step C13: forming aSchottky layer 43 on the channel layer 42; and Step C14: forming a caplayer 44 on the Schottky layer 43. Step C2 includes following steps of:Step C21: (Please referring to FIG. 3E) defining a gate electrodeetching area, and etching to remove the cap layer 44 within the gateelectrode etching area such that the etching stops at the Schottky layer43 to form a gate recess 451, thereby the Schottky layer 43 within thegate recess 451 is exposed; Step C22: (Please referring to FIG. 3F)forming a drain electrode 47 on one end of the cap layer 44; Step C23:forming a source electrode 46 on the other end of the cap layer 44,wherein the gate recess 451 is located between the drain electrode 47and the source electrode 46; and Step C24: forming a gate electrode 45on the Schottky layer 43 within the gate recess 451. Step C3 includesfollowing steps of: Step C31: (Please referring to FIG. 3G) forming atop sacrificial layer 63 on the compound semiconductor epitaxialsubstrate 10 (the cap layer 44); Step C32: defining a top sacrificiallayer etching area, and etching to remove the top sacrificial layer 63within the top sacrificial layer etching area to form a top sacrificiallayer mesa 632, such that the compound semiconductor epitaxial substrate10 (the cap layer 44) within the top sacrificial layer etching area isexposed; Step C33: (Please referring to FIGS. 3H and 3I) forming asupporting layer 61 on the top sacrificial layer 63 and the compoundsemiconductor epitaxial substrate 10 (the cap layer 44), wherein thesupporting layer 61 has a supporting layer mesa 611 right above the topsacrificial layer mesa 632; wherein the supporting layer 61 may also beformed on the gate electrode 45, the source electrode 46, the drainelectrode 47 and the gate recess 451, where the supporting layer 61plays a role of protection; Step C34: forming a bulk acoustic resonatorstructure 60 on the supporting layer 61, which includes following stepsof: Step C341: (Please referring to FIG. 3J) forming a bottom electrode601 on one end of the supporting layer 61, where the bottom electrode601 is formed on and at least extended along the supporting layer mesa611; Step C342: (Please referring to FIG. 3K) forming a dielectric layer602, wherein the dielectric layer 602 is formed at least on the bottomelectrode 601 above the supporting layer mesa 611; and Step C343:(Please referring to FIG. 3L) forming a top electrode 603, wherein thetop electrode 603 is formed on the other end with respect to the bottomelectrode 601, where the top electrode 603 is formed on the dielectriclayer 602 or formed on both the dielectric layer 602 and the supportinglayer 61, and the top electrode 603 is formed on and at least extendedalong the dielectric layer 602 above the supporting layer mesa 611; StepC35: defining at least one recess etching area, and etching to removethe supporting layer 61 within the at least one recess etching area oretching to remove the supporting layer 61 and the bulk acousticresonator structure 60 within the at least one recess etching area suchthat the etching stops at the top sacrificial layer mesa 632 and/or thecompound semiconductor epitaxial substrate 10 (the cap layer 44) to format least one etching recess 62, thereby part of the top sacrificiallayer mesa 632 is exposed (Please referring to FIGS. 3L and 3M, whereinthe cross-sectional direction of FIG. 3M is orthogonal to that of FIG.3L, and there is only the acoustic wave device 50 at the position of thecross-sectional direction of FIG. 3M, hence there is no power amplifier20 shown in FIG. 3M); Step C36: etching to remove the top sacrificiallayer mesa 632 to form a supporting layer recess 612, wherein at leastone top sacrificial layer etching solution contacts with the topsacrificial layer mesa 632 via the at least one etching recess 62 andetches to remove the top sacrificial layer mesa 632, thereby the top andthe bottom of the supporting layer recess 612 are the supporting layer61 and the compound semiconductor epitaxial substrate 10 (the cap layer44) respectively (Please referring to FIGS. 3N and 3O, wherein thecross-sectional direction of FIG. 3O is orthogonal to that of FIG. 3N,and there is only the acoustic wave device 50 at the position of thecross-sectional direction of FIG. 3O, hence there is no power amplifier20 shown in FIG. 3O); and Step C37: etching to remove part of thecompound semiconductor epitaxial substrate 10 below the supporting layerrecess 612 to form a substrate recess 15 (Please referring to FIGS. 3Aand 3C, wherein the cross-sectional direction of FIG. 3C is orthogonalto that of FIG. 3A, and there is only the acoustic wave device 50 at theposition of the cross-sectional direction of FIG. 3C, hence there is nopower amplifier 20 shown in FIG. 3C), wherein at least one substraterecess etching solution contacts with the top surface of the compoundsemiconductor epitaxial substrate 10 (the cap layer 44) via the at leastone etching recess 62 and the supporting layer recess 612, the at leastone substrate recess etching solution is uniformly distributed on thetop surface of the compound semiconductor epitaxial substrate 10 (thecap layer 44) through the supporting layer recess 612 so as to uniformlyetch part of the compound semiconductor epitaxial substrate 10 below thesupporting layer recess 612 to form the substrate recess 15, and therebyprevents the side etching phenomenon during the etching, wherein thesupporting layer recess 612 is communicated with the substrate recess15, and the supporting layer recess 612 and the substrate recess 15 havea boundary 103 therebetween and the boundary 103 is the extended fromthe top surface of the compound semiconductor epitaxial substrate 10,wherein the gap between the supporting layer mesa 611 and the bottom ofthe substrate recess 15 is increased by the communication of thesupporting layer recess 612 and the substrate recess 15, so as to avoidthe contact of the supporting layer mesa 611 and the bottom of thesubstrate recess 15 when the film bulk acoustic resonator 51 is affectedby stress such that the supporting layer mesa 611 is bended downwardly;thereby the left part 101 of the compound semiconductor epitaxialsubstrate 10 includes: the compound semiconductor substrate 12, thebuffer layer 41, the channel layer 42, the Schottky layer 43, the caplayer 44 and the gate recess 451; the power amplifier upper structure 21includes: the drain electrode 47, the source electrode 46 and the gateelectrode 45; wherein the left part 101 of the compound semiconductorepitaxial substrate 10 and the power amplifier upper structure 21 formthe pseudomorphic high electron mobility transistor 40; wherein thebottom of the substrate recess 15 is the compound semiconductorepitaxial substrate 10 (the buffer layer 41), and the substrate recess15 is peripherally surrounded by the channel layer 42, the Schottkylayer 43 and the cap layer 44 or by the buffer layer 41, the channellayer 42, the Schottky layer 43 and the cap layer 44 (Please referringto FIG. 3B).

Please refer to FIG. 4, the cross-sectional view of an embodiment of theimproved acoustic wave device structure of the present invention, theimproved acoustic wave device structure comprises: a substrate 11 and afilm bulk acoustic resonator 51; wherein the substrate 11 has asubstrate recess 15 on the top of the substrate 11; the film bulkacoustic resonator 51 is formed on the substrate 11; wherein the filmbulk acoustic resonator 51 includes: a supporting layer 61 and a bulkacoustic resonator structure 60; wherein supporting layer 61 is formedon the substrate 11, wherein the supporting layer 61 has a supportinglayer recess 612 on the bottom of the supporting layer 61, thesupporting layer 61 has an upwardly protruding supporting layer mesa 611right above the supporting layer recess 612, and the supporting layerrecess 612 is located right above the substrate recess 15, thesupporting layer recess 612 is communicated with the substrate recess15, and the supporting layer recess 612 and the substrate recess 15 havea boundary 113 therebetween and the boundary 113 is the extended fromthe top surface of the substrate 11; the bulk acoustic resonatorstructure 60 is formed on the supporting layer 61, wherein the bulkacoustic resonator structure 60 includes: a bottom electrode 601, adielectric layer 602 and a top electrode 603. The bottom electrode 601is formed on one end of the supporting layer 61, where the bottomelectrode 601 is formed on and at least extended along the supportinglayer mesa 611. The dielectric layer 602 is formed at least on thebottom electrode 601 above the supporting layer mesa 611. In theembodiment of FIG. 4, the dielectric layer 602 is formed on both thebottom electrode 601 and the supporting layer 61, and the dielectriclayer 602 is also formed on the bottom electrode 601 above thesupporting layer mesa 611. Please also refer to FIG. 4A, which shows thecross-sectional view of another embodiment of the improved acoustic wavedevice structure of the present invention. The main structure in FIG. 4Ais basically the same as the structure shown in FIG. 4, except that thedielectric layer 602 is formed on the bottom electrode 601 above thesupporting layer mesa 611 and on a small part of the supporting layer 61above the supporting layer mesa 611. The top electrode 603 is formed onthe other end with respect to the bottom electrode 601, where the topelectrode 603 is formed on the dielectric layer 602 or formed on boththe dielectric layer 602 and the supporting layer 61, and the topelectrode 603 is formed on and at least extended along the dielectriclayer 602 above the supporting layer mesa 611. In the embodiment of FIG.4, the top electrode 603 is formed on the dielectric layer 602, while inembodiment of FIG. 4A, the top electrode 603 is formed on both thedielectric layer 602 and the supporting layer 61. The top electrode 603and the bottom electrode 601 are not electrically connected. The gapbetween the supporting layer mesa 611 and the bottom of the substraterecess 15 is increased by the communication of the supporting layerrecess 612 and the substrate recess 15, so as to avoid the contact ofthe supporting layer mesa 611 and the bottom of the substrate recess 15when the film bulk acoustic resonator 51 is affected by stress such thatthe supporting layer mesa 611 is bended downwardly.

In an embodiment, the application of the acoustic wave device 50 may bea filter. Usually plural acoustic wave devices 50 are in series and/orin parallel in the combination of circuit to form a filter which mayfilter the signal.

In one embodiment, the application of the acoustic wave device 50 may bea mass sensing device, a biomedical sensing device, an UV sensingdevice, a pressure sensing device or a temperature sensing device.

In an embodiment, the function of the supporting layer 61 may be thesupporting for the film bulk acoustic resonator 51 for preventing thefilm bulk acoustic resonator 51 from collapsing. The supporting layer 61also may be the seed layer for the bottom electrode 601 and thedielectric layer 602 for improving the crystalline quality. In anembodiment, the supporting layer 61 is made of SiN_(x) or AlN. Thesupporting layer 61 is formed on the substrate 11 by molecular beamepitaxy (MBE), sputtering or chemical vapor deposition (CVD).

In an embodiment, the bottom electrode 601 is needed to have a lowerroughness and resistivity for benefit the preferable crystal growthaxis. In an embodiment, the bottom electrode 601 is made of Mo, Pt, Al,Au, W or Ru. The bottom electrode 601 is formed on the supporting layer61 by evaporation or sputtering.

In an embodiment, the dielectric layer 602 is made of AlN,monocrystalline SiO₂, ZnO, HfO₂, barium strontium titanate (BST) or leadzirconate titanate (PZT), and is formed on the bottom electrode 601 orformed on both the electrode 601 and the supporting layer 61 byepitaxial growth or sputtering. The selection of the materials of thedielectric layer 602 is associated with the application. AlN is a highacoustic wave velocity material (12000 m/s) and is suitable for highfrequency application, and after the formation of the micro structure ofthe material, it has good physical and chemical stability and itsproperties are not easily to be influenced by the circumstance. ZnO maybe formed under lower temperature and it has an acoustic wave velocity6000 m/s. Its electromechanical coupling coefficient is higher (8.5%)and it is suitable for the application of broadband filter. However whenforming ZnO, the concentration of oxygen vacancies in ZnO is not easilycontrolled, yet it is easily influenced by the humidity and oxygen ofthe circumstance. Both barium strontium titanate (BST) and leadzirconate titanate (PZT) are ferroelectric materials. Their dielectricconstant may vary under external electric field. Hence, they aresuitable for the application of acoustic wave device with tunablefrequency within dozen MHz range of frequencies. Both barium strontiumtitanate (BST) and lead zirconate titanate (PZT) need to be polarizedunder high voltage electric field in order to obtain their piezoelectriccharacteristics. Lead zirconate titanate (PZT) has higherelectromechanical coupling coefficient, however it contains lead.

In an embodiment, the top electrode 603 is needed to have a lowerresistivity for reducing power loss so as to reduce the insertion loss.In an embodiment, the top electrode 603 may be made of Mo, Pt, Al, Au, Wor Ru. The top electrode 603 is formed on the dielectric layer 602 or isformed on both the dielectric layer 602 and the supporting layer 61 byevaporation or sputtering.

In an embodiment, the bottom electrode 601 is made of Mo or Pt, whilethe dielectric layer 602 is made of AlN. The Mo of the bottom electrode601 may be etched by Lithography and Lift-off process. And the AlN ofthe dielectric layer 602 may be etched by inductively coupled plasma(ICP) process with CF₄ plasma.

In an embodiment, the depth of the substrate recess 15 is between 50 nmand 10000 nm.

In an embodiment, the depth of the supporting layer recess 612 isbetween 10 nm and 3500 nm. In another embodiment, the optimized depth ofthe supporting layer recess 612 is between 10 nm and 1500 nm.

Please refer to FIG. 4B, which shows the cross-sectional view of anotherembodiment of the improved acoustic wave device structure of the presentinvention. The main structure in FIG. 4B is basically the same as thestructure shown in FIG. 4, except that the film bulk acoustic resonator51 further comprises at least one etching recess 62. The cross-sectionaldirection of FIG. 4B is orthogonal to that of FIG. 4. One end of the atleast one etching recess 62 is communicated with the supporting layerrecess 612, the other end of the at least one etching recess 62penetrates the supporting layer 61 or penetrates both the supportinglayer 61 and the bulk acoustic resonator structure 60 such that the atleast one etching recess 62 is communicated with the outside, andthereby the supporting layer recess 612 is communicated with theoutside.

Please refer to FIG. 4C, which shows the partial enlargedcross-sectional view of an embodiment of the improved acoustic wavedevice structure of the present invention. In the embodiment of FIG. 4C,the supporting layer recess 612 has an opening smaller than that of thesubstrate recess 15. Please refer to FIG. 4D, which shows the partialenlarged cross-sectional view of another embodiment of the improvedacoustic wave device structure of the present invention. In theembodiment of FIG. 4D, the supporting layer recess 612 has an openingalmost equal to that of the substrate recess 15.

Please refer to FIGS. 4E, 4F, 4G and 4H, which show the top views of therelative position of the etching recess and the supporting layer mesa inthe embodiments of the improved acoustic wave device structure of thepresent invention. In the embodiment of FIG. 4E, the improved acousticwave device structure 50 has two etching recess 62 with long stripopening. The two etching recesses 62 are located on two opposite sidesof the supporting layer mesa 611 respectively. And the etching recesses62 penetrate the supporting layer 61 (not shown in FIG. 4E), and therebythe supporting layer recess 612 (not shown in FIG. 4E) is communicatedwith the outside. In the embodiment of FIG. 4F, the improved acousticwave device structure 50 has two etching recess 62 with long stripopening. The two etching recesses 62 are located on two opposite sidesof the supporting layer mesa 611 respectively. (part of the etchingrecesses 62 are within the supporting layer mesa 611, the rest part ofthe etching recesses 62 are outside the supporting layer mesa 611) Andthe etching recesses 62 penetrate the supporting layer 61 (not shown inFIG. 4F) and the dielectric layer 602. In the embodiment of FIG. 4Q theimproved acoustic wave device structure 50 has two etching recess 62with long strip opening. The two etching recesses 62 are locatedrespectively on two opposite sides of the supporting layer mesa 611within the supporting layer mesa 611. And the etching recesses 62penetrate the supporting layer 61 (not shown in FIG. 4G), the bottomelectrode 601, the dielectric layer 602 and the top electrode 603. Inthe embodiment of FIG. 4H, the improved acoustic wave device structure50 has four etching recess 62 with square opening. The four etchingrecesses 62 are located on four corners of the supporting layer mesa 611respectively. And the etching recesses 62 penetrate the supporting layer61 (not shown in FIG. 4H). The amount of the etching recesses 62 is notlimited to one, two, three, four or more. The etching recesses 62 maylocate on other position and should not be limited by FIG. 4E, 4F, 4G or4H.

Please refer to FIG. 5, which shows the cross-sectional view of anotherembodiment of the improved acoustic wave device structure of the presentinvention. The main structure in FIG. 5 is basically the same as thestructure shown in FIG. 4, except that the substrate 11 includes a basesubstrate 16 and an epitaxial structure 13 formed on the base substrate16. The epitaxial structure 13 includes: a buffer layer 41, an etchingstop layer 32 and a bottom sacrificial layer 65; wherein the bufferlayer 41 is formed on the base substrate 16; the etching stop layer 32is formed on the buffer layer 41; the bottom sacrificial layer 65 isformed on the etching stop layer 32; wherein the substrate recess 15 isperipherally surrounded by the bottom sacrificial layer 65, and thebottom of the substrate recess 15 is the etching stop layer 32.

In an embodiment, the base substrate 16 may be made of GaAs, SiC, InP,GaN, AlN, Sapphire, Si or glass.

In an embodiment, the buffer layer 41 is made of GaAs, SiO₂ or GaN andis formed on the base substrate 16 by epitaxial growth.

In an embodiment, the base substrate 16 is made of GaAs, while thebuffer layer 41 is preferable to be made of GaAs. In another embodiment,the base substrate 16 is made of Sapphire, while the buffer layer 41 ispreferable to be made of GaN. In one embodiment, the base substrate 16is made of Si, while the buffer layer 41 is preferable to be made ofSiO₂.

In an embodiment, the etching stop layer 32 is made of InGaP. In oneembodiment, the thickness of the etching stop layer 32 is between 5 nmand 1000 nm. In another embodiment, the optimized thickness of theetching stop layer 32 is 20 nm.

In an embodiment, the bottom sacrificial layer 65 is made of GaAs and isformed on the etching stop layer 32 by molecular beam epitaxy (MBE) ormetal organic chemical vapor deposition (MOCVD). In another embodiment,the thickness of the bottom sacrificial layer 65 is between 500 nm and3000 nm.

In an embodiment, the buffer layer 41 is made of GaAs, SiO₂ or GaN. Thebottom sacrificial layer 65 is made of GaAs, Phosphosilicate glass (PSG)or Borophosphosilicate glass (BPSG). The etching stop layer 32 is madeof InGaP, SiN_(x), Pt, Al or Au.

In an embodiment, the bottom sacrificial layer 65 is made of GaAs; theetching stop layer 32 is made of InGaP; GaAs of the bottom sacrificiallayer 65 may be etched by citric acid; and the etching may stop at InGaPof the etching stop layer 32. In another embodiment, the bottomsacrificial layer 65 is made of Phosphosilicate glass (PSG) orBorophosphosilicate glass (BPSG); the etching stop layer 32 is made ofSiN_(x), Pt, Al or Au.

Please refer to FIG. 5A, which shows the cross-sectional view of anotherembodiment of the improved acoustic wave device structure of the presentinvention. The main structure in FIG. 5A is basically the same as thestructure shown in FIG. 5, except that the film bulk acoustic resonator51 further comprises at least one etching recess 62. The cross-sectionaldirection of FIG. 5A is orthogonal to that of FIG. 5. One end of the atleast one etching recess 62 is communicated with the supporting layerrecess 612, the other end of the at least one etching recess 62penetrates the supporting layer 61 or penetrates both the supportinglayer 61 and the bulk acoustic resonator structure 60 such that the atleast one etching recess 62 is communicated with the outside, andthereby the supporting layer recess 612 is communicated with theoutside. The feature of the at least one etching recess 62 of theembodiment in FIG. 5A is basically the same as that of the embodiment inFIG. 4B.

Please refer to FIGS. 5B and 5C. The cross-sectional direction of FIG.5C is orthogonal to that of FIG. 5B. The present invention provides afabrication method for improved acoustic wave device structure. Thefabrication method for the embodiment of FIGS. 5B and 5C comprisesfollowing steps of: Step D1: forming an epitaxial structure 13 on a basesubstrate 16 to form a substrate 11; and Step D2: forming a film bulkacoustic resonator 51 on the substrate 11 (the epitaxial structure 13).Step D1 includes following steps of: Step D11: (Please referring to FIG.5D) forming a buffer layer 41 on the base substrate 16; Step D12:forming an etching stop layer 32 on the buffer layer 41; and Step D13:forming a bottom sacrificial layer 65 on the etching stop layer 32;wherein the epitaxial structure 13 includes: the buffer layer 41, theetching stop layer 32 and the bottom sacrificial layer 65. Step D2includes following steps of: Step D21: (Please referring to FIG. 5D)forming a top sacrificial layer 63 on the substrate 11 (the bottomsacrificial layer 65); Step D22: (Please referring to FIG. 5E) defininga top sacrificial layer etching area, and etching to remove the topsacrificial layer 63 within the top sacrificial layer etching area toform a top sacrificial layer mesa 632, such that the substrate 11 (thebottom sacrificial layer 65) within the top sacrificial layer etchingarea is exposed; Step D23: forming a supporting layer 61 on the topsacrificial layer 63 and the substrate 11 (the bottom sacrificial layer65), wherein the supporting layer 61 has a supporting layer mesa 611right above the top sacrificial layer mesa 632 (Please referring toFIGS. 5F and 5Q wherein the cross-sectional direction of FIG. 5G isorthogonal to that of FIG. 5F); wherein after Step D23, it may alsochoose to execute the step: defining a supporting layer etching area,and etching to remove the supporting layer 61 within the supportinglayer etching area, such that the top sacrificial layer mesa 632 and/orthe substrate 11 (the bottom sacrificial layer 65) within the supportinglayer etching area are/is exposed (please also referring to FIGS. 5H and5I, wherein the cross-sectional direction of FIG. 5I is orthogonal tothat of FIG. 5H); Step D24: forming a bulk acoustic resonator structure60 on the supporting layer 61 (Please referring to FIGS. 5J and 5K,wherein the cross-sectional direction of FIG. 5K is orthogonal to thatof FIG. 5J), which includes following steps of: Step D241: forming abottom electrode 601 on one end of the supporting layer 61, where thebottom electrode 601 is formed on and at least extended along thesupporting layer mesa 611; Step D242: forming a dielectric layer 602,wherein the dielectric layer 602 is formed at least on the bottomelectrode 601 above the supporting layer mesa 611; and Step D243:forming a top electrode 603, wherein the top electrode 603 is formed onthe other end with respect to the bottom electrode 601, where the topelectrode 603 is formed on the dielectric layer 602 or formed on boththe dielectric layer 602 and the supporting layer 61, and the topelectrode 603 is formed on and at least extended along the dielectriclayer 602 above the supporting layer mesa 611; Step D25: defining atleast one recess etching area, and etching to remove the supportinglayer 61 within the at least one recess etching area or etching toremove the supporting layer 61 and the bulk acoustic resonator structure60 within the at least one recess etching area such that the etchingstops at the top sacrificial layer mesa 632 and/or the substrate 11 (thebottom sacrificial layer 65) to form at least one etching recess 62,thereby part of the top sacrificial layer mesa 632 is exposed; Step D26:etching to remove the top sacrificial layer mesa 632 to form asupporting layer recess 612, wherein at least one top sacrificial layeretching solution contacts with the top sacrificial layer mesa 632 viathe at least one etching recess 62 and etches to remove the topsacrificial layer mesa 632, thereby the top and the bottom of thesupporting layer recess 612 are the supporting layer 61 and thesubstrate 11 (the bottom sacrificial layer 65) respectively (Pleasereferring to FIGS. 5L and 5M, wherein the cross-sectional direction ofFIG. 5M is orthogonal to that of FIG. 5L); and Step D27: etching toremove part of the substrate 11 below the supporting layer recess 612 toform a substrate recess 15 (Please referring to FIGS. 5B and 5C, whereinthe cross-sectional direction of FIG. 5C is orthogonal to that of FIG.5B), wherein the substrate recess 15 is peripherally surrounded by thebottom sacrificial layer 65, and the bottom of the substrate recess 15is the etching stop layer 32, wherein at least one substrate recessetching solution contacts with the top surface of the substrate 11 viathe at least one etching recess 62 and the supporting layer recess 612,the at least one substrate recess etching solution is uniformlydistributed on the top surface of the substrate 11 through thesupporting layer recess 612 so as to uniformly etch part of thesubstrate 11 below the supporting layer recess 612 to form the substraterecess 15, and thereby prevents the side etching phenomenon during theetching, wherein the supporting layer recess 612 is communicated withthe substrate recess 15, and the supporting layer recess 612 and thesubstrate recess 15 have a boundary 113 therebetween and the boundary113 is the extended from the top surface of the substrate 11, whereinthe gap between the supporting layer mesa 611 and the bottom of thesubstrate recess 15 is increased by the communication of the supportinglayer recess 612 and the substrate recess 15, so as to avoid the contactof the supporting layer mesa 611 and the bottom of the substrate recess15 when the film bulk acoustic resonator 51 is affected by stress suchthat the supporting layer mesa 611 is bended downwardly.

In an embodiment, the top sacrificial layer 63 is made of AlAs or TiW.

In an embodiment, the TiW of the top sacrificial layer 63 may be formedby sputtering on the epitaxial structure 13. TiW may be etched by H₂O₂.

In an embodiment, the AlAs of the top sacrificial layer 63 may be formedby molecular beam epitaxy (MBE) or metal organic chemical vapordeposition (MOCVD) on the epitaxial structure 13.

In an embodiment, the thickness of the top sacrificial layer 63 isbetween 10 nm and 3500 nm. In another embodiment, the optimizedthickness of the top sacrificial layer 63 is between 10 nm and 1500 nm.

Please refer to FIG. 6, which shows the cross-sectional view of anotherembodiment of the improved acoustic wave device structure of the presentinvention. The main structure in FIG. 6 is basically the same as thestructure shown in FIG. 4, except that the substrate 11 is a siliconsubstrate 14.

In another embodiment, the substrate 11 is a glass substrate.

Please refer to FIG. 6A, which shows the cross-sectional view of anotherembodiment of the improved acoustic wave device structure of the presentinvention. The main structure in FIG. 6A is basically the same as thestructure shown in FIG. 6, except that the film bulk acoustic resonator51 further comprises at least one etching recess 62. The cross-sectionaldirection of FIG. 6A is orthogonal to that of FIG. 6. One end of the atleast one etching recess 62 is communicated with the supporting layerrecess 612, the other end of the at least one etching recess 62penetrates the supporting layer 61 or penetrates both the supportinglayer 61 and the bulk acoustic resonator structure 60 such that the atleast one etching recess 62 is communicated with the outside, andthereby the supporting layer recess 612 is communicated with theoutside. The feature of the at least one etching recess 62 of theembodiment in FIG. 6A is basically the same as that of the embodiment inFIG. 4B.

Please refer to FIGS. 6 and 6A. The cross-sectional direction of FIG. 6Ais orthogonal to that of FIG. 6. The present invention provides afabrication method for improved acoustic wave device structure. Thefabrication method for the embodiment of FIGS. 6 and 6A comprisesfollowing steps of: Step E1: forming a film bulk acoustic resonator 51on a substrate 11, which includes following steps of: Step E11: (Pleasereferring to FIG. 6B) forming a top sacrificial layer 63 on thesubstrate 11, wherein the substrate 11 is a silicon substrate 14; StepE12: (Please referring to FIG. 6C) defining a top sacrificial layeretching area, and etching to remove the top sacrificial layer 63 withinthe top sacrificial layer etching area to form a top sacrificial layermesa 632, such that the substrate 11 within the top sacrificial layeretching area is exposed; Step E13: forming a supporting layer 61 on thetop sacrificial layer 63 and the substrate 11, wherein the supportinglayer 61 has a supporting layer mesa 611 right above the top sacrificiallayer mesa 632 (Please referring to FIGS. 6D and 6E, wherein thecross-sectional direction of FIG. 6E is orthogonal to that of FIG. 6D);wherein after Step E13, it may also choose to execute the step: defininga supporting layer etching area, and etching to remove the supportinglayer 61 within the supporting layer etching area, such that the topsacrificial layer mesa 632 and/or the substrate 11 within the supportinglayer etching area are/is exposed (please also referring to FIGS. 6F and6G wherein the cross-sectional direction of FIG. 6G is orthogonal tothat of FIG. 6F); Step E14: forming a bulk acoustic resonator structure60 on the supporting layer 61 (Please referring to FIGS. 6H and 6I,wherein the cross-sectional direction of FIG. 6I is orthogonal to thatof FIG. 6H), which includes following steps of: Step E141: forming abottom electrode 601 on one end of the supporting layer 61, where thebottom electrode 601 is formed on and at least extended along thesupporting layer mesa 611; Step E142: forming a dielectric layer 602,wherein the dielectric layer 602 is formed at least on the bottomelectrode 601 above the supporting layer mesa 611; and Step E143:forming a top electrode 603, wherein the top electrode 603 is formed onthe other end with respect to the bottom electrode 601, where the topelectrode 603 is formed on the dielectric layer 602 or formed on boththe dielectric layer 602 and the supporting layer 61, and the topelectrode 603 is formed on and at least extended along the dielectriclayer 602 above the supporting layer mesa 611; Step E15: defining atleast one recess etching area, and etching to remove the supportinglayer 61 within the at least one recess etching area or etching toremove the supporting layer 61 and the bulk acoustic resonator structure60 within the at least one recess etching area such that the etchingstops at the top sacrificial layer mesa 632 and/or the substrate 11 toform at least one etching recess 62, thereby part of the top sacrificiallayer mesa 632 is exposed; Step E16: etching to remove the topsacrificial layer mesa 632 to form a supporting layer recess 612,wherein at least one top sacrificial layer etching solution contactswith the top sacrificial layer mesa 632 via the at least one etchingrecess 62 and etches to remove the top sacrificial layer mesa 632,thereby the top and the bottom of the supporting layer recess 612 arethe supporting layer 61 and the substrate 11 respectively (Pleasereferring to FIGS. 6J and 6K, wherein the cross-sectional direction ofFIG. 6K is orthogonal to that of FIG. 6J); and Step E17: etching toremove part of the substrate 11 below the supporting layer recess 612 toform a substrate recess 15 (Please referring to FIGS. 6 and 6A, whereinthe cross-sectional direction of FIG. 6A is orthogonal to that of FIG.6), wherein the bottom of the substrate recess 15 is the substrate 11,wherein at least one substrate recess etching solution contacts with thetop surface of the substrate 11 via the at least one etching recess 62and the supporting layer recess 612, the at least one substrate recessetching solution is uniformly distributed on the top surface of thesubstrate 11 through the supporting layer recess 612 so as to uniformlyetch part of the substrate 11 below the supporting layer recess 612 toform the substrate recess 15, and thereby prevents the side etchingphenomenon during the etching, wherein the supporting layer recess 612is communicated with the substrate recess 15, and the supporting layerrecess 612 and the substrate recess 15 have a boundary 113 therebetweenand the boundary 113 is the extended from the top surface of thesubstrate 11, wherein the gap between the supporting layer mesa 611 andthe bottom of the substrate recess 15 is increased by the communicationof the supporting layer recess 612 and the substrate recess 15, so as toavoid the contact of the supporting layer mesa 611 and the bottom of thesubstrate recess 15 when the film bulk acoustic resonator 51 is affectedby stress such that the supporting layer mesa 611 is bended downwardly.

In another embodiment, the substrate 11 is a silicon substrate 14, thetop sacrificial layer 63 is made of TiW.

In an embodiment, the TiW of the top sacrificial layer 63 may be formedby sputtering on the substrate 11. TiW may be etched by H₂O₂.

In an embodiment, the thickness of the top sacrificial layer 63 isbetween 10 nm and 3500 nm. In another embodiment, the optimizedthickness of the top sacrificial layer 63 is between 10 nm and 1500 nm.

Please refer to FIGS. 6M and 6N, which show the cross-sectional views ofanother embodiment of the improved acoustic wave device structure of thepresent invention, wherein the cross-sectional direction of FIG. 6N isorthogonal to that of FIG. 6M. The main structure in FIGS. 6M and 6N isbasically the same as the structure shown in FIGS. 6 and 6A, except thatin Step E12 (Please compare FIGS. 6C and 6L), the top sacrificial layer63 is etched and removed, except the top sacrificial layer mesa 632.

As disclosed in the above description and attached drawings, the presentinvention can provide an improved acoustic wave device structure, anintegrated structure of power amplifier and acoustic wave device, andfabrication methods thereof with reduced component size, optimized theimpedance matching, and reduced the signal loss between the poweramplifier and the acoustic wave device. It is new and can be put intoindustrial use.

Although the embodiments of the present invention have been described indetail, many modifications and variations may be made by those skilledin the art from the teachings disclosed hereinabove. Therefore, itshould be understood that any modification and variation equivalent tothe spirit of the present invention be regarded to fall into the scopedefined by the appended claims.

What is claimed is:
 1. An integrated structure of power amplifier andacoustic wave device, comprising: a compound semiconductor epitaxialsubstrate including a compound semiconductor substrate and an epitaxialstructure formed on said compound semiconductor substrate; a poweramplifier upper structure formed on a top-side of a left part of saidcompound semiconductor epitaxial substrate, wherein said left part ofsaid compound semiconductor epitaxial substrate and said power amplifierupper structure form a power amplifier; and a film bulk acousticresonator formed on said top-side of a right part of said compoundsemiconductor epitaxial substrate, wherein said right part of saidcompound semiconductor epitaxial substrate and said film bulk acousticresonator form an acoustic wave device, wherein said film bulk acousticresonator comprises: a supporting layer formed on said compoundsemiconductor epitaxial substrate, wherein said supporting layer has asupporting layer recess on the bottom of said supporting layer, saidsupporting layer has an upwardly protruding supporting layer mesa rightabove said supporting layer recess, and wherein said compoundsemiconductor epitaxial substrate has a substrate recess on the top ofsaid compound semiconductor epitaxial substrate, said substrate recessis located right below said supporting layer recess, said supportinglayer recess is communicated with said substrate recess, and saidsupporting layer recess and said substrate recess have a boundarytherebetween and the boundary is the extended from the top surface ofsaid compound semiconductor epitaxial substrate; and a bulk acousticresonator structure formed on said supporting layer, wherein said bulkacoustic resonator structure includes: a bottom electrode formed on oneend of said supporting layer, where said bottom electrode is formed onand at least extended along said supporting layer mesa; a dielectriclayer formed at least on said bottom electrode above said supportinglayer mesa; and a top electrode formed on the other end with respect tosaid bottom electrode, where said top electrode is formed on saiddielectric layer or formed on both said dielectric layer and saidsupporting layer, and said top electrode is formed on and at leastextended along said dielectric layer above said supporting layer mesa;wherein the gap between said supporting layer mesa and the bottom ofsaid substrate recess is increased by the communication of saidsupporting layer recess and said substrate recess, so as to avoid thecontact of said supporting layer mesa and the bottom of said substraterecess when said film bulk acoustic resonator is affected by stress suchthat said supporting layer mesa is bended downwardly; wherein, theintegrated structure of said power amplifier and said acoustic wavedevice on the same said compound semiconductor epitaxial substrate iscapable of reducing the component size, optimizing the impedancematching, and reducing the signal loss between said power amplifier andsaid acoustic wave device.
 2. The integrated structure of poweramplifier and acoustic wave device according to claim 1, wherein saidsupporting layer recess has a depth between 10 nm and 3500 nm.
 3. Theintegrated structure of power amplifier and acoustic wave deviceaccording to claim 2, wherein said supporting layer recess has a depthbetween 10 nm and 1500 nm.
 4. The integrated structure of poweramplifier and acoustic wave device according to claim 1, wherein saidsupporting layer recess has an opening smaller than or almost equal tothat of said substrate recess.
 5. The integrated structure of poweramplifier and acoustic wave device according to claim 1, wherein saidfilm bulk acoustic resonator further comprises at least one etchingrecess, one end of said at least one etching recess is communicated withsaid supporting layer recess, the other end of said at least one etchingrecess penetrates said supporting layer or penetrates both saidsupporting layer and said bulk acoustic resonator structure such thatsaid at least one etching recess is communicated with the outside, andthereby said supporting layer recess is communicated with the outside.6. An integrated structure of power amplifier and acoustic wave device,comprising: a compound semiconductor epitaxial substrate including acompound semiconductor substrate and an epitaxial structure formed onsaid compound semiconductor substrate, wherein said epitaxial structureincludes: a subcollector layer formed on said compound semiconductorsubstrate; and a collector layer formed on said subcollector layer; apower amplifier upper structure formed on a top-side of a left part ofsaid compound semiconductor epitaxial substrate, wherein said left partof said compound semiconductor epitaxial substrate and said poweramplifier upper structure form a power amplifier, wherein said poweramplifier is a heterojunction bipolar transistor (HBT), wherein saidleft part of said compound semiconductor epitaxial substrate furthercomprises a collector recess, the bottom of said collector recess issaid subcollector layer, and wherein said power amplifier upperstructure includes: a base layer formed on said collector layer; anemitter ledge layer formed on said base layer; an emitter layer formedon said emitter ledge layer; a base electrode formed on said base layerand/or said emitter ledge layer; an emitter electrode formed on saidemitter layer; and a collector electrode formed on said subcollectorlayer within said collector recess; thereby said left part of saidcompound semiconductor epitaxial substrate includes: said compoundsemiconductor substrate, said subcollector layer, said collector layerand said collector recess; wherein said left part of said compoundsemiconductor epitaxial substrate and said power amplifier upperstructure form said heterojunction bipolar transistor; and a film bulkacoustic resonator formed on said top-side of a right part of saidcompound semiconductor epitaxial substrate, wherein said right part ofsaid compound semiconductor epitaxial substrate and said film bulkacoustic resonator form an acoustic wave device; wherein, the integratedstructure of said power amplifier and said acoustic wave device on thesame said compound semiconductor epitaxial substrate is capable ofreducing the component size, optimizing the impedance matching, andreducing the signal loss between said power amplifier and said acousticwave device.
 7. The integrated structure of power amplifier and acousticwave device according to claim 6, wherein said collector layer is madeof GaAs.
 8. The integrated structure of power amplifier and acousticwave device according to claim 6, wherein said collector layer has athickness between 500 nm and 3000 nm.
 9. The integrated structure ofpower amplifier and acoustic wave device according to claim 6, whereinsaid base layer is made of GaAs.
 10. The integrated structure of poweramplifier and acoustic wave device according to claim 6, wherein saidbase layer has a thickness between 60 nm and 100 nm.
 11. The integratedstructure of power amplifier and acoustic wave device according to claim6, wherein said epitaxial structure further comprises an etching stoplayer, wherein said etching stop layer is formed on said subcollectorlayer, and said collector layer is formed on said etching stop layer,wherein the bottom of said collector recess is said subcollector layer,said collector electrode is formed on said subcollector layer withinsaid collector recess.
 12. The integrated structure of power amplifierand acoustic wave device according to claim 11, wherein said substraterecess is peripherally surrounded by said collector layer and saidetching stop layer, and the bottom of said substrate recess is saidsubcollector layer.
 13. The integrated structure of power amplifier andacoustic wave device according to claim 11, wherein said etching stoplayer is made of InGaP.
 14. The integrated structure of power amplifierand acoustic wave device according to claim 11, wherein said etchingstop layer has a thickness between 5 nm and 1000 nm.
 15. The integratedstructure of power amplifier and acoustic wave device according to claim14, wherein said etching stop layer has a thickness 20 nm.
 16. Anintegrated structure of power amplifier and acoustic wave device,comprising: a compound semiconductor epitaxial substrate including acompound semiconductor substrate and an epitaxial structure formed onsaid compound semiconductor substrate, wherein said epitaxial structureincludes: a buffer layer formed on said compound semiconductorsubstrate; a channel layer formed on said buffer layer; a Schottky layerformed on said channel layer; and a cap layer formed on said Schottkylayer; a power amplifier upper structure formed on a top-side of a leftpart of said compound semiconductor epitaxial substrate, wherein saidleft part of said compound semiconductor epitaxial substrate and saidpower amplifier upper structure form a power amplifier, wherein saidpower amplifier is a field effect transistor (FET), a high electronmobility transistor (HEMT) or a pseudomorphic high electron mobilitytransistor (pHEMT); and a film bulk acoustic resonator formed on saidtop-side of a right part of said compound semiconductor epitaxialsubstrate, wherein said right part of said compound semiconductorepitaxial substrate and said film bulk acoustic resonator form anacoustic wave device; wherein, the integrated structure of said poweramplifier and said acoustic wave device on the same said compoundsemiconductor epitaxial substrate is capable of reducing the componentsize, optimizing the impedance matching, and reducing the signal lossbetween said power amplifier and said acoustic wave device.
 17. Theintegrated structure of power amplifier and acoustic wave deviceaccording to claim 16, wherein the bottom of said substrate recess issaid buffer layer, and said substrate recess is peripherally surroundedby said channel layer, said Schottky layer and said cap layer or by saidbuffer layer, said channel layer, said Schottky layer and said caplayer.
 18. The integrated structure of power amplifier and acoustic wavedevice according to claim 16, wherein said left part of said compoundsemiconductor epitaxial substrate further comprises a gate recess, thebottom of said gate recess is said Schottky layer, and wherein saidpower amplifier upper structure includes: a drain electrode formed onone end of said cap layer; a source electrode formed on the other end ofsaid cap layer, wherein said gate recess is located between said drainelectrode and said source electrode; and a gate electrode formed on saidSchottky layer within said gate recess; thereby said left part of saidcompound semiconductor epitaxial substrate includes: said compoundsemiconductor substrate, said buffer layer, said channel layer, saidSchottky layer, said cap layer and said gate recess; wherein said leftpart of said compound semiconductor epitaxial substrate and said poweramplifier upper structure form said pseudomorphic high electron mobilitytransistor.
 19. The integrated structure of power amplifier and acousticwave device according to claim 1, wherein said compound semiconductorsubstrate is made of GaAs, SiC, InP, GaN, AlN or Sapphire.
 20. Animproved acoustic wave device structure comprises: a substrate having asubstrate recess on the top of said substrate; and a film bulk acousticresonator formed on said substrate, wherein said film bulk acousticresonator includes: a supporting layer formed on said substrate, whereinsaid supporting layer has a supporting layer recess on the bottom ofsaid supporting layer, said supporting layer has an upwardly protrudingsupporting layer mesa right above said supporting layer recess, and saidsupporting layer recess is located right above said substrate recess,said supporting layer recess is communicated with said substrate recess,and said supporting layer recess and said substrate recess have aboundary therebetween and the boundary is the extended from the topsurface of said substrate; and a bulk acoustic resonator structureformed on said supporting layer, wherein said bulk acoustic resonatorstructure includes: a bottom electrode formed on one end of saidsupporting layer, where said bottom electrode is formed on and at leastextended along said supporting layer mesa; a dielectric layer formed atleast on said bottom electrode above said supporting layer mesa; and atop electrode formed on the other end with respect to said bottomelectrode, where said top electrode is formed on said dielectric layeror formed on both said dielectric layer and said supporting layer, andsaid top electrode is formed on and at least extended along saiddielectric layer above said supporting layer mesa; wherein the gapbetween said supporting layer mesa and the bottom of said substraterecess is increased by the communication of said supporting layer recessand said substrate recess, so as to avoid the contact of said supportinglayer mesa and the bottom of said substrate recess when said film bulkacoustic resonator is affected by stress such that said supporting layermesa is bended downwardly.
 21. The improved acoustic wave devicestructure according to claim 20, wherein said substrate includes a basesubstrate and an epitaxial structure formed on said base substrate. 22.The improved acoustic wave device structure according to claim 21,wherein said base substrate is made of GaAs, SiC, InP, GaN, AlN,Sapphire, Si or glass.
 23. The improved acoustic wave device structureaccording to claim 21, wherein said epitaxial structure includes: abuffer layer formed on said base substrate; an etching stop layer formedon said buffer layer; and a bottom sacrificial layer formed on saidetching stop layer; wherein said substrate recess is peripherallysurrounded by said bottom sacrificial layer, and the bottom of saidsubstrate recess is said etching stop layer.
 24. The improved acousticwave device structure according to claim 23, wherein said bottomsacrificial layer is made of GaAs.
 25. The improved acoustic wave devicestructure according to claim 23, wherein said bottom sacrificial layerhas a thickness between 500 nm and 3000 nm.
 26. The improved acousticwave device structure according to claim 23, wherein said etching stoplayer is made of InGaP.
 27. The improved acoustic wave device structureaccording to claim 23, wherein said etching stop layer has a thicknessbetween 5 nm and 1000 nm.
 28. The improved acoustic wave devicestructure according to claim 27, wherein said etching stop layer has athickness 20 nm.
 29. The improved acoustic wave device structureaccording to claim 20, wherein said substrate is made of a siliconsubstrate.
 30. The improved acoustic wave device structure according toclaim 20, wherein said supporting layer recess has a depth between 10 nmand 3500 nm.
 31. The improved acoustic wave device structure accordingto claim 30, wherein said supporting layer recess has a depth between 10nm and 1500 nm.
 32. The improved acoustic wave device structureaccording to claim 20, wherein said film bulk acoustic resonator furthercomprises at least one etching recess, one end of said at least oneetching recess is communicated with said supporting layer recess, theother end of said at least one etching recess penetrates said supportinglayer or penetrates both said supporting layer and said bulk acousticresonator structure such that said at least one etching recess iscommunicated with the outside, and thereby said supporting layer recessis communicated with the outside.
 33. The improved acoustic wave devicestructure according to claim 20, wherein said supporting layer recesshas an opening smaller than or almost equal to that of said substraterecess.
 34. The integrated structure of power amplifier and acousticwave device according to claim 6, wherein said compound semiconductorsubstrate is made of GaAs, SiC, InP, GaN, AlN or Sapphire.
 35. Theintegrated structure of power amplifier and acoustic wave deviceaccording to claim 16, wherein said compound semiconductor substrate ismade of GaAs, SiC, InP, GaN, AN or Sapphire.